Add DevkitPPC support

DevkitPPC does not support unix sockets natively, meaning that bindings
to these functions was removed for powerpc targets with "nintendo" as
vendor

Suggested target json files:

Nintendo Gamecube:
```
{
  "arch": "powerpc",
  "data-layout": "E-m:e-p:32:32-i64:64-n32",
  "dynamic-linking": false,
  "env": "newlib",
  "executables": true,
  "has-elf-tls": false,
  "has-rpath": true,
  "linker-flavor": "gcc",
  "llvm-target": "powerpc-eabi",
  "max-atomic-width": 32,
  "os": "dolphin",
  "target-c-int-width": "32",
  "target-endian": "big",
  "target-family": "unix",
  "target-mcount": "_mcount",
  "target-pointer-width": "32",
  "vendor": "nintendo"
}
```

Nintendo Wii:
```
{
  "arch": "powerpc",
  "data-layout": "E-m:e-p:32:32-i64:64-n32",
  "dynamic-linking": false,
  "env": "newlib",
  "executables": true,
  "has-elf-tls": false,
  "has-rpath": true,
  "linker-flavor": "gcc",
  "llvm-target": "powerpc-eabi",
  "max-atomic-width": 32,
  "os": "revolution",
  "target-c-int-width": "32",
  "target-endian": "big",
  "target-family": "unix",
  "target-mcount": "_mcount",
  "target-pointer-width": "32",
  "vendor": "nintendo"
}
```

Author: Dark Kirb

src/unix/mod.rs

@@ -596,9 +596,11 @@ extern "C" {
     pub fn getchar_unlocked() -> ::c_int;
     pub fn putchar_unlocked(c: ::c_int) -> ::c_int;
 
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     #[cfg_attr(target_os = "netbsd", link_name = "__socket30")]
     #[cfg_attr(target_os = "illumos", link_name = "__xnet_socket")]
     pub fn socket(domain: ::c_int, ty: ::c_int, protocol: ::c_int) -> ::c_int;
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     #[cfg_attr(
         all(target_os = "macos", target_arch = "x86"),
         link_name = "connect$UNIX2003"
@@ -614,6 +616,7 @@ extern "C" {
         link_name = "listen$UNIX2003"
     )]
     pub fn listen(socket: ::c_int, backlog: ::c_int) -> ::c_int;
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     #[cfg_attr(
         all(target_os = "macos", target_arch = "x86"),
         link_name = "accept$UNIX2003"
@@ -623,6 +626,7 @@ extern "C" {
         address: *mut sockaddr,
         address_len: *mut socklen_t,
     ) -> ::c_int;
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     #[cfg_attr(
         all(target_os = "macos", target_arch = "x86"),
         link_name = "getpeername$UNIX2003"
@@ -632,6 +636,7 @@ extern "C" {
         address: *mut sockaddr,
         address_len: *mut socklen_t,
     ) -> ::c_int;
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     #[cfg_attr(
         all(target_os = "macos", target_arch = "x86"),
         link_name = "getsockname$UNIX2003"
@@ -659,6 +664,7 @@ extern "C" {
         protocol: ::c_int,
         socket_vector: *mut ::c_int,
     ) -> ::c_int;
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     #[cfg_attr(
         all(target_os = "macos", target_arch = "x86"),
         link_name = "sendto$UNIX2003"
@@ -1234,13 +1240,15 @@ extern "C" {
     pub fn dlclose(handle: *mut ::c_void) -> ::c_int;
     pub fn dladdr(addr: *const ::c_void, info: *mut Dl_info) -> ::c_int;
 
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     #[cfg_attr(target_os = "illumos", link_name = "__xnet_getaddrinfo")]
     pub fn getaddrinfo(
         node: *const c_char,
         service: *const c_char,
         hints: *const addrinfo,
         res: *mut *mut addrinfo,
     ) -> ::c_int;
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     pub fn freeaddrinfo(res: *mut addrinfo);
     pub fn gai_strerror(errcode: ::c_int) -> *const ::c_char;
     #[cfg_attr(

src/unix/newlib/mod.rs

@@ -33,11 +33,13 @@ s! {
         pub ai_protocol: ::c_int,
         pub ai_addrlen: socklen_t,
 
+        #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
         #[cfg(target_arch = "xtensa")]
         pub ai_addr: *mut sockaddr,
 
         pub ai_canonname: *mut ::c_char,
 
+        #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
         #[cfg(not(target_arch = "xtensa"))]
         pub ai_addr: *mut sockaddr,
 
@@ -598,6 +600,7 @@ extern "C" {
     pub fn rand() -> ::c_int;
     pub fn srand(seed: ::c_uint);
 
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     pub fn bind(fd: ::c_int, addr: *const sockaddr, len: socklen_t)
         -> ::c_int;
     pub fn clock_settime(
@@ -614,6 +617,7 @@ extern "C" {
     ) -> ::c_int;
     pub fn closesocket(sockfd: ::c_int) -> ::c_int;
     pub fn ioctl(fd: ::c_int, request: ::c_ulong, ...) -> ::c_int;
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     pub fn recvfrom(
         fd: ::c_int,
         buf: *mut ::c_void,
@@ -622,6 +626,7 @@ extern "C" {
         addr: *mut sockaddr,
         addr_len: *mut socklen_t,
     ) -> isize;
+    #[cfg(not(all(target_arch = "powerpc", target_vendor = "nintendo")))]
     pub fn getnameinfo(
         sa: *const sockaddr,
         salen: socklen_t,
@@ -700,6 +705,9 @@ cfg_if! {
     } else if #[cfg(target_arch = "xtensa")] {
         mod xtensa;
         pub use self::xtensa::*;
+    } else if #[cfg(target_arch = "powerpc")] {
+        mod powerpc;
+        pub use self::powerpc::*;
     } else {
         // Only tested on ARM so far. Other platforms might have different
         // definitions for types and constants.

src/unix/newlib/powerpc/mod.rs

@@ -0,0 +1,14 @@
+pub type clock_t = ::c_ulong;
+pub type c_char = u8;
+pub type wchar_t = ::c_int;
+
+pub type c_long = i32;
+pub type c_ulong = u32;
+
+// the newlib shipped with devkitPPC does not support the following components:
+// - sockaddr
+// - AF_INET6
+// - FIONBIO
+// - POLL*
+// - SOL_SOCKET
+// - MSG_*