Allow make-gnucash-potfiles to run from directories other than srcdir.

Better documentation of exactly what m-g-potfiles excludes, and a general
   clean-up of the script.


git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@13079 57a11ea4-9604-0410-9ed3-97b8803252fd

Makefile.am

@@ -92,6 +92,7 @@ make-gnucash-patch: make-gnucash-patch.in Makefile
 make-gnucash-potfiles: make-gnucash-potfiles.in Makefile
 	rm -f $@.tmp
 	sed < $< > $@.tmp \
+            -e 's:@-SRCDIR-@:${srcdir}:g' \
             -e 's:@-PERL-@:${PERL}:g'
 	chmod +x $@.tmp
 	mv $@.tmp $@