PR-108557 Stuck compilation for empty file

PR-108557 Stuck compilation for empty file

Trying to compile an empty file causes cc1gm2 to hang.
The bug occurs when M2LexBuf.mod calls m2flex.GetToken after
an eof token has been seen which results in m2flex attempting
to read from stdin.  The bug fix detects eof per file and
blocks subsequent calls to m2flex.GetToken.

gcc/m2/ChangeLog:

	* gm2-compiler/M2Comp.mod:  Import MetaString0.
	(ExamineCompilationUnit): New variable Message.
	Create and format error string.
	* gm2-compiler/M2LexBuf.mod: New variable SeenEof.
	(GetNonEofToken): New procedure.
	(Init): Set SeenEof to FALSE.
	(GetToken): Use GetNonEofToken instead of calls to
	m2flex.GetToken and GetToken.
	(AddTok): Detect eoftok and set SeenEof.

gcc/testsuite/ChangeLog:

	* gm2/pim/fail/empty.mod: New test.

Signed-off-by: Gaius Mulley <gaiusmod2@gmail.com>