Define macros for renaming xmalloc and xcalloc

I'm planning to link strace with libiberty for mangling C++
symbol names in stack trace enabled with -k option.

Both names, xmalloc and xcalloc, are already defined and used
in libiberty, and they conflict with functions in strace.
Rename xmalloc and xcalloc functions defined in strace
to strace_xmalloc and strace_xcalloc, respectively,
to avoid this conflict.

* xmalloc.h (xcalloc, xmalloc): New macros.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>

xmalloc.h

@@ -36,6 +36,9 @@
 #include <stddef.h>
 #include "gcc_compat.h"
 
+#define xcalloc strace_calloc
+#define xmalloc strace_malloc
+
 void *xcalloc(size_t nmemb, size_t size)
 	ATTRIBUTE_MALLOC ATTRIBUTE_ALLOC_SIZE((1, 2));
 void *xmalloc(size_t size) ATTRIBUTE_MALLOC ATTRIBUTE_ALLOC_SIZE((1));