PR c/54428
	* c-convert.c (convert): Don't call fold_convert_loc if
	TYPE_MAIN_VARIANT of a COMPLEX_TYPE is the same, unless e
	is a COMPLEX_EXPR.  Remove TYPE_MAIN_VARIANT check from
	COMPLEX_TYPE -> COMPLEX_TYPE conversion.

	* gcc.c-torture/compile/pr54428.c: New test.

From-SVN: r190840