perl: avoid *.pmc and fix Error.pm further

The previous round tried to use *.pmc files but it confused RPM
dependency analysis on some distros.  Install them as plain
vanilla *.pm files instead.

Also "local @_" construct did not properly work when goto &sub
is used until recent versions of Perl.  Avoid it (and we do not
need to localize it here anyway).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

perl/Git/Error.pm

@@ -39,7 +39,7 @@ sub import {
 	require Error;
     };
 
-    local @_ = ($caller, @_);
+    unshift @_, $caller;
     goto &Error::import;
 }