ada: Small cleanup in support for protected subprograms

ada: Small cleanup in support for protected subprograms

This moves the propagation of the Uses_Sec_Stack flag, from the original to
the rewritten subprogram, to the point where the latter is expanded, along
with the propagation of the Has_Nested_Subprogram flag, as well as addresses
a ??? comment in the same block of code.  No functional changes.

gcc/ada/

	* inline.adb (Cleanup_Scopes): Do not propagate the Uses_Sec_Stack
	flag from original to rewritten protected subprograms here...
	* exp_ch9.adb (Expand_N_Protected_Body) <N_Subprogram_Body>:
	...but here instead. Add local variables and remove a useless
	test.