Move global state in timevar.c to a new "timer" class

gcc/ChangeLog:
	* timevar.c (timevar_enable): Delete in favor of...
	(g_timer): New global.
	(struct timevar_def): Move to timevar.h inside class timer.
	(struct timevar_stack_def): Likewise.
	(timevars): Delete global in favor of field "m_timevars" within
	class timer in timevar.h
	(stack): Likewise, in favor of field "m_stack".
	(unused_stack_instances): Likewise, in favor of field
	"m_unused_stack_instances".
	(start_time): Likewise, in favor of field "m_start_time".
	(get_time): Eliminate check for timevar_enable.
	(timer::timer): New function, built from part of timevar_init.
	(timevar_init): Rewrite idempotency test from using
	"timevar_enable" bool to using dynamic allocation of "g_timer".
	Move rest of implementation into timer's constructor.
	(timevar_push_1): Rename to...
	(timer::push): ...this, adding "m_" prefixes to variables that
	are now fields of timer.
	(timevar_pop_1): Likewise, rename to...
	(timer::pop): ...this, and add "m_" prefixes.
	(timevar_start): Replace test for "timevar_enable" with one for
	"g_timer", and move bulk of implementation to...
	(timer::start): ...here, adding "m_" prefixes.
	(timevar_stop): Likewise, from here...
	(timer::stop): ...to here.
	(timevar_cond_start): Likewise, from here...
	(timer::cond_start): ...to here.
	(timevar_cond_stop): Likewise, from here...
	(timer::cond_stop): ...to here.
	(validate_phases): Rename to...
	(timer::validate_phases): ...this, and add "m_" prefixes.  Make
	locals "total" and "tv" const.
	(timevar_print): Rename to...
	(timer::print): ...this, and add "m_" prefixes.  Make locals
	"total" and "tv" const.  Eliminate test for timevar_enable.
	* timevar.h (timevar_enable): Eliminate.
	(g_timer): New declaration.
	(timevar_push_1): Eliminate.
	(timevar_pop_1): Eliminate.
	(timevar_print): Eliminate.
	(class timer): New class.
	(timevar_push): Rewrite to use g_timer.
	(timevar_pop): Likewise.
	* toplev.c (toplev::~toplev): Likewise.

From-SVN: r223092