Bugfix for segfault in stubs library

[tlwilmar]

Summary

There was a segfault in the stubs library in posix_memalign because
of a bad parameter. The fix is to send address of the pointer as a
parameter. Also added check of result of posix_memalign.

Patch by Andrey Churbanov.

[hbae]

LGTM.

openmp/trunk/runtime/src/kmp_stub.c

 /* KMP memory management functions. */
 void * kmp_malloc( size_t size )                 { i; return malloc( size ); }
 void * kmp_aligned_malloc( size_t sz, size_t a ) {
     i;
 #if KMP_OS_WINDOWS
     errno = ENOSYS; // not supported
     return NULL;    // no standard aligned allocator on Windows (pre - C11)
 #else
-    void **res;
-    errno = posix_memalign( res, a, sz );
-    return *res;
+    void *res;
+    int err;
+    if( err = posix_memalign( &res, a, sz ) ) {
+        errno = err; // can be EINVAL or ENOMEM
+        return NULL;
+    }
+    return res;
 #endif
 }
 void * kmp_calloc( size_t nelem, size_t elsize ) { i; return calloc( nelem, elsize ); }
 void * kmp_realloc( void *ptr, size_t size )     { i; return realloc( ptr, size ); }
 void   kmp_free( void * ptr )                    { i; free( ptr ); }
 
 static int __kmps_blocktime = INT_MAX;