gmmproc: Discard unused m4 sections
gmmproc: Discard unused m4 sections

tools/m4/base.m4: At the end of the _END macro, discard all remaining sections.
m4_divert(-1) + m4_undivert() was probably meant to do just that, but it does
nothing. m4_divert(-1) + m4_undivert, without parentheses, discards all
remaining sections. Bug #756593

GNOME/glibmm,GNOME/glibmm,GNOME/glibmm,GNOME/glibmm,GNOME/glibmm