analyzer: use known_function to simplify region_model::on_call_{pre,post}

Replace lots of repeated checks against strings with a hash_map lookup.
Add some missing type-checking for handling known functions (e.g. checks
for pointer types).

gcc/analyzer/ChangeLog:
	* analyzer.h (known_function::matches_call_types_p): New vfunc.
	(known_function::impl_call_pre): Provide base implementation.
	(known_function::impl_call_post): New vfunc.
	(register_known_functions): New.
	* engine.cc (impl_run_checkers): Call register_known_functions.
	* region-model-impl-calls.cc (region_model::impl_call_accept):
	Convert to...
	(class known_function_accept): ...this.
	(region_model::impl_call_bind): Convert to...
	(class known_function_bind): ...this.
	(region_model::impl_call_connect): Convert to...
	(class known_function_connect): ...this.
	(region_model::impl_call_listen): Convert to...
	(class known_function_listen): ...this.
	(region_model::impl_call_socket): Convert to...
	(class known_function_socket): ...this.
	(register_known_functions): New.
	* region-model.cc (region_model::on_call_pre): Remove special
	case for "bind" in favor of the known_function-handling dispatch.
	Add call to known_function::matches_call_types_p to latter.
	(region_model::on_call_post): Remove special cases for "accept",
	"bind", "connect", "listen", and "socket" in favor of dispatch
	to known_function::impl_call_post.
	* region-model.h (region_model::impl_call_accept): Delete decl.
	(region_model::impl_call_bind): Delete decl.
	(region_model::impl_call_connect): Delete decl.
	(region_model::impl_call_listen): Delete decl.
	(region_model::impl_call_socket): Delete decl.
	* sm-fd.cc: Update comments.

gcc/testsuite/ChangeLog:
	* gcc.dg/plugin/analyzer_kernel_plugin.c
	(copy_across_boundary_fn::matches_call_types_p): New.
	* gcc.dg/plugin/analyzer_known_fns_plugin.c
	(known_function_returns_42::matches_call_types_p): New.
	(known_function_attempt_to_copy::matches_call_types_p): New.

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