uemacs: Add xmalloc as a wrapper function for malloc.

xmalloc checks the returned pointer and dies if it failed to allocate
the memory.

Use this new function in window.c.
More places will be converted to use xmalloc latter.

Signed-off-by: Thiago Farina <tfransosi@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
3 files changed