Build fails with recent glibc due to outdated gnulib

[Brandon Invergo]

Building m4 fails with recent versions of glibc (2.16+). The error
occurs in a file pulled in from gnulib:

In file included from clean-temp.h:22:0,
                 from clean-temp.c:23:
./stdio.h:477:1: error: 'gets' undeclared here (not in a function)
make[4]: *** [clean-temp.o] Error 1
make[4]: Leaving directory 
`/home/brandon/Projects/gsrc/gsrc/trunk/gnu/m4/work/m4-1.4.16/lib'

The error exists in this file:
lib/stdio.in.h

The problem has already been fixed upstream in gnulib[1], so it should be
as simple as updating the code included in m4.

Cheers,
Brandon Invergo

[1] https://lists.gnu.org/archive/html/bug-gnulib/2012-03/msg00186.html