pass_manager: add m_ prefix to pass fields accessed via passes.def

pass_manager: add m_ prefix to pass fields accessed via passes.def

Make it clearer when we're accessing member data of pass_manager by
adding an "m"_ prefix to the fields handled via passes.def macros.

No functional change intended.

gcc/ChangeLog:
	* pass_manager.h (class pass_manager): Add "m_" prefix to all pass
	fields.
	* passes.cc (pass_manager::execute_early_local_passes): Update
	for added "m_" prefix.
	(pass_manager::execute_pass_mode_switching): Likewise.
	(pass_manager::finish_optimization_passes): Likewise.
	(pass_manager::pass_manager): Likewise.
	(pass_manager::dump_profile_report): Likewise.

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