Merge #34: win32: fix -Wmissing-field-initializers warnings

12c52b3 win32: fix -Wmissing-field-initializers warnings (fanquake)

Pull request description:

  When building with `-Wmissing-field-initializers`, the following warning is emitted:
  ```bash
  leveldb/util/env_windows.cc: In member function ‘virtual leveldb::Status leveldb::{anonymous}::WindowsRandomAccessFile::Read(uint64_t, size_t, leveldb::Slice*, char*) const’:
  leveldb/util/env_windows.cc:197:31: warning: missing initializer for member ‘_OVERLAPPED::InternalHigh’ [-Wmissing-field-initializers]
    197 |     OVERLAPPED overlapped = {0};
        |                               ^
  leveldb/util/env_windows.cc:197:31: warning: missing initializer for member ‘_OVERLAPPED::<anonymous>’ [-Wmissing-field-initializers]
  leveldb/util/env_windows.cc:197:31: warning: missing initializer for member ‘_OVERLAPPED::hEvent’ [-Wmissing-field-initializers]
  ```

  Submitted upstream: google#1053

ACKs for top commit:
  sipsorcery:
    ACK 12c52b3.
  hebasto:
    ACK 12c52b3, I have reviewed the code and it looks OK.
  theuni:
    ACK 12c52b3

Tree-SHA512: be8590f37c21af2ed5e77ebd5fdf6c5da1cba1e72c46c241202b4dfbcd3667e1aa2522b303eaa9c1e5d6a61290dd268e76c0a1e42df6bf5734c775ca6b2dbdf2

Author: fanquake

util/env_windows.cc

@@ -194,7 +194,7 @@ class WindowsRandomAccessFile : public RandomAccessFile {
   Status Read(uint64_t offset, size_t n, Slice* result,
               char* scratch) const override {
     DWORD bytes_read = 0;
-    OVERLAPPED overlapped = {0};
+    OVERLAPPED overlapped = {};
 
     overlapped.OffsetHigh = static_cast<DWORD>(offset >> 32);
     overlapped.Offset = static_cast<DWORD>(offset);