Introduce two new test suites under test/api/: return_double exercises wrenReturnDouble with integer and floating-point values, and return_null verifies that a foreign function returning nothing yields null. Refactor bindForeign dispatch in main.c to use a REGISTER_TEST macro, rename returnBoolBindForeign to return_boolBindForeign for consistency, and add an exit(1) on unknown foreign methods to prevent silent NULL returns.
Bob Nystrom
3297642b65