GNUmakefile and 'make install'

[Eric Blake]

I've pushed a commit that syncs to the latest gnulib version of GNUmakefile.  
The difference is that if you type 'make install' in a git checkout, the 
makefile now checks that your version string is up-to-date before proceeding 
with the installation (rather than the former behavior of installing with a 
possibly old string, such that version-based tests like AC_PREREQ([2.62.10]) 
could fail even though your git checkout is new enough).  If it is out of date, 
the error message reminds you to run 'autoreconf' to pick up the corrected 
version string (running 'make dist' would do the same); per GNU Coding 
Standards, 'make install' does not in and of itself recompile to pick up the 
new version string.  This should have no impact on tarball users, only on 
people working on autoconf.git.

-- 
Eric Blake