analyzer work on issues with flex-generated lexers [PR103546]

PR analyzer/103546 tracks various false positives seen on
flex-generated lexers.

Whilst investigating them, I noticed an ICE with
-fanalyzer-call-summaries due to attempting to store sm-state
for an UNKNOWN svalue, which this patch fixes.

This patch also provides known_function implementations of all of the
external functions called by the lexer, reducing the number of false
positives.

The patch doesn't eliminate all false positives, but adds integration
tests to try to establish a baseline from which the remaining false
positives can be fixed.

gcc/analyzer/ChangeLog:
	PR analyzer/103546
	* analyzer.h (register_known_file_functions): New decl.
	* program-state.cc (sm_state_map::replay_call_summary): Rejct
	attempts to store sm-state for caller_sval that can't have
	associated state.
	* region-model-impl-calls.cc (register_known_functions): Call
	register_known_file_functions.
	* sm-fd.cc (class kf_isatty): New.
	(register_known_fd_functions): Register it.
	* sm-file.cc (class kf_ferror): New.
	(class kf_fileno): New.
	(class kf_getc): New.
	(register_known_file_functions): New.

gcc/ChangeLog:
	PR analyzer/103546
	* doc/invoke.texi (Static Analyzer Options): Add isatty, ferror,
	fileno, and getc to the list of functions known to the analyzer.

gcc/testsuite/ChangeLog:
	PR analyzer/103546
	* gcc.dg/analyzer/ferror-1.c: New test.
	* gcc.dg/analyzer/fileno-1.c: New test.
	* gcc.dg/analyzer/flex-with-call-summaries.c: New test.
	* gcc.dg/analyzer/flex-without-call-summaries.c: New test.
	* gcc.dg/analyzer/getc-1.c: New test.
	* gcc.dg/analyzer/isatty-1.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>