Emacs should work with gcc 5.2 and newer

Emacs should work with gcc 5.2 and newer

This patch, backported from upstream by Aurelien Jarno
<aurel32@debian.org>, has been added:

  Always define gmalloc etc. in src/gmalloc.c

  This is a work-around to prevent the compiler from using semantic
  knowledge about malloc for optimization purposes.  E.g., gcc 5.2
  with -O2 replaces most of calloc's definition by a call to calloc;
  see Bug#22085.
  * src/gmalloc.c [!HYBRID_MALLOC] (malloc, realloc, calloc)
  (aligned_alloc, free): Do not undef.  Instead, define these as
  functions (perhaps renamed to gmalloc etc.) in terms of gmalloc etc.

Origin: backport, commit: 4b1436b702d56eedd27a0777fc7232cdfb7ac4f6
Bug-Debian: http://bugs.debian.org/833727
Added-by: Rob Browning <rlb@defaultvalue.org>