cleanup: use internal memory allocation wrapper functions everywhere

The "x"-prefixed versions of strdup, malloc, etc. will check whether the
allocation was successful and terminate the process otherwise.

A few uses of malloc were left alone since they already implemented a
graceful path of failure or were in a quasi external library like xdiff.

Additionally, the call to malloc in compat/win32/syslog.c was not modified
since the syslog() implemented there is a die handler and a call to the
x-wrappers within a die handler could result in recursion should memory
allocation fail.  This will have to be addressed separately.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/show-index.c b/show-index.c
index 4c0ac13..63f9da5 100644
--- a/show-index.c
+++ b/show-index.c
@@ -48,7 +48,7 @@
 			unsigned char sha1[20];
 			uint32_t crc;
 			uint32_t off;
-		} *entries = malloc(nr * sizeof(entries[0]));
+		} *entries = xmalloc(nr * sizeof(entries[0]));
 		for (i = 0; i < nr; i++)
 			if (fread(entries[i].sha1, 20, 1, stdin) != 1)
 				die("unable to read sha1 %u/%u", i, nr);