Remove (near-)duplicate definitions of size_t and ssize_t.

The near duplicates upset fussier compilers that insist that
typedefs be exactly the same, but the fix isn't to make all
copies identical...

Change-Id: Icfdace41726f36ec33c9ae919dbb5a54d3529cc9

libc/include/sys/types.h

@@ -83,11 +83,6 @@ typedef  .... pthread_rwlock_attr_t;
 typedef  .... pthread_t;
 #endif
 
-#ifndef _SIZE_T_DEFINED_
-#define _SIZE_T_DEFINED_
-typedef unsigned int  size_t;
-#endif
-
 #ifndef _SSIZE_T_DEFINED_
 #define _SSIZE_T_DEFINED_
 typedef long int  ssize_t;