libcc1: Fix tags generation target

libcc1: Fix tags generation target

'make tags' currently fails for libcc1 with this:
 *** No rule to make target `marshall-c.hh', needed by `tags-am'.  Stop.

The problem is that while marshall-c.hh has been removed via
r12-454-g25d1a6ecdc443f, it's still part of the libcc1_la_SOURCES
variable, hence the 'tags' target has a dependency on it.

This patch simply removes the marshall_c_source variable, that should be
empty.

libcc1/ChangeLog:

	* Makefile.am: Remove reference to deleted marshall-c.h.
	* Makefile.in: Regenerate.