analyzer: simplify region_model::push_frame

analyzer: simplify region_model::push_frame

region_model::push_frame was binding arguments for both the default SSA
name for each parameter, and the underlying parameter.

Simplify the generated states by only binding the default SSA name if
it exists, or the parameter if there is no default SSA name.

gcc/analyzer/ChangeLog:
	* region-model.cc (region_model::push_frame): Bind the default
	SSA name for each parm if it exists, falling back to the parm
	itself otherwise, rather than doing both.

gcc/testsuite/ChangeLog:
	* gcc.dg/analyzer/malloc-ipa-8-double-free.c: Drop
	-fanalyzer-verbose-state-changes.