compiler warning in req_wait.c

```
request/req_wait.c: In function 'ompi_request_default_wait_any':
request/req_wait.c:146:16: warning: comparison between signed and unsigned integer 
expressions [-Wsign-compare]
     if( *index == completed ){
                ^
runtime/ompi_mpi_init.c:121:2: warning: #ident is a GCC extension
```

@thananon Can you please fix?  Thanks.
