c++: extend cold, hot attributes to classes

c++: extend cold, hot attributes to classes

Most code is cold. This patch extends support for attribute ((cold)) to C++
Classes, Unions, and Structs (RECORD_TYPES and UNION_TYPES) to benefit from
encapsulation - reducing the verbosity of using the attribute where
deserved. The ((hot)) attribute is also extended for its semantic relation.

gcc/c-family/ChangeLog:

	* c-attribs.cc (handle_hot_attribute): remove warning on
	RECORD_TYPE and UNION_TYPE when in c_dialect_xx.
	(handle_cold_attribute): Likewise.

gcc/cp/ChangeLog:

	* class.cc (propagate_class_warmth_attribute): New function.
	(check_bases_and_members): propagate hot and cold attributes
	to all FUNCTION_DECL when the record is marked hot or cold.
	* cp-tree.h (maybe_propagate_warmth_attributes): New function.
	* decl2.cc (maybe_propagate_warmth_attributes): New function.
	* method.cc (lazily_declare_fn): propagate hot and cold
	attributes to lazily declared functions when the record is
	marked hot or cold.

gcc/ChangeLog:

	* doc/extend.texi: Document attributes hot, cold on C++ types.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/attr-hotness.C: New test.

Signed-off-by: Javier Martinez <javier.martinez.bugzilla@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>