Clean up <stdlib.h> slightly.

Interestingly, this mostly involves cleaning up our implementation of
various <string.h> functions.

Change-Id: Ifaef49b5cb997134f7bc0cc31bdac844bdb9e089
diff --git a/libc/Android.mk b/libc/Android.mk
index a2a3108..691017a 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -271,7 +271,6 @@
     upstream-freebsd/lib/libc/string/wcsspn.c \
     upstream-freebsd/lib/libc/string/wcstok.c \
     upstream-freebsd/lib/libc/string/wmemchr.c \
-    upstream-freebsd/lib/libc/string/wmemcpy.c \
     upstream-freebsd/lib/libc/string/wmemset.c \
 
 libc_upstream_netbsd_src_files := \
@@ -506,6 +505,7 @@
     upstream-openbsd/lib/libc/string/strspn.c \
     upstream-openbsd/lib/libc/string/strstr.c \
     upstream-openbsd/lib/libc/string/strtok.c \
+    upstream-openbsd/lib/libc/string/wmemcpy.c \
     upstream-openbsd/lib/libc/string/wcslcpy.c \
     upstream-openbsd/lib/libc/string/wcsstr.c \
     upstream-openbsd/lib/libc/string/wcswidth.c \