Remove Xcalloc/Xmalloc/Xfree calls

Remove Xcalloc/Xmalloc/Xfree calls

These calls allowed Xlib to use a custom memory allocator, but Xlib has
used the standard C library functions since at least its initial import
into git in 2003. It seems unlikely that it will grow a custom memory
allocator. The functions now just add extra overhead. Replacing them
will make future Coccinelle patches simpler.

This patch has been generated by the following Coccinelle semantic
patch:

// Remove Xcalloc/Xmalloc/Xfree calls

@@ expression E1, E2; @@
- Xcalloc (E1, E2)
+ calloc (E1, E2)

@@ expression E; @@
- Xmalloc (E)
+ malloc (E)

@@ expression E; @@
- Xfree (E)
+ free (E)

@@ expression E; @@
- XFree (E)
+ free (E)

Reviewed-by: Brian Paul <brianp@vmware.com>