Merge branch 'ab/simplify-perl-makefile'

The build procedure for perl/ part has been greatly simplified by
weaning ourselves off of MakeMaker.

* ab/simplify-perl-makefile:
  perl: treat PERLLIB_EXTRA as an extra path again
  perl: avoid *.pmc and fix Error.pm further
  Makefile: replace perl/Makefile.PL with simple make rules

perl/Git.pm

@@ -101,7 +101,7 @@ increase notwithstanding).
 
 
 use Carp qw(carp croak); # but croak is bad - throw instead
-use Error qw(:try);
+use Git::Error qw(:try);
 use Cwd qw(abs_path cwd);
 use IPC::Open2 qw(open2);
 use Fcntl qw(SEEK_SET SEEK_CUR);