C: Drop qualifiers during lvalue conversion [PR97702]

2020-11-20  Martin Uecker  <muecker@gwdg.de>

gcc/
	* gimplify.c (gimplify_modify_expr_rhs): Optimizie
	NOP_EXPRs that contain compound literals.

gcc/c/
	* c-typeck.c (convert_lvalue_to_rvalue): Drop qualifiers.

gcc/testsuite/
	* gcc.dg/cond-constqual-1.c: Adapt test.
	* gcc.dg/lvalue-11.c: New test.
	* gcc.dg/pr60195.c: Add warning.