c++, coroutines: Clean up the ramp cleanups.

c++, coroutines: Clean up the ramp cleanups.

This replaces the cleanup try-catch block in the ramp with a series of
eh-only cleanup statements.

gcc/cp/ChangeLog:

	* coroutines.cc
	(cp_coroutine_transform::build_ramp_function): Replace ramp
	cleanup try-catch block with eh-only cleanup statements.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>