maint: address a couple of syntax-check errors.

maint: address a couple of syntax-check errors.

	* cfg.mk (local-checks-to-skip): Remove sc_error_message_period
	and sc_error_message_uppercase.
	Address the uncovered issues.
	* po/POTFILES.in: Add missing files.
	* src/symtab.c: Remove useless includes.
	* lib/bitset_stats.c, src/files.c, tests/glr-regression.at: Use
	conformant error messages.

Conflicts:

	cfg.mk
	lib/bitset_stats.c
	tests/glr-regression.at