macrocall: Specialize macro invocations like normal function calls

`jl_invoke` behaves like `Expr(:invoke, ...)` not `Core.invoke`, so we
were (accidentally?) bypassing the default specialization for a `macro`
and only ever invoked de-specialized MethodInstances.

Change this to `jl_apply` so that we specialize as normal, which should
dramatically improve inference and not lead to much extra code since our
AST is very homogeneous (`Expr` + typeof.(literals), IIUC)

Author: topolarity

src/ast.c

@@ -1135,7 +1135,7 @@ static jl_value_t *jl_invoke_julia_macro(jl_array_t *args, jl_module_t *inmodule
         }
         jl_timing_show_macro(mfunc, margs[1], inmodule, JL_TIMING_DEFAULT_BLOCK);
         *ctx = mfunc->def.method->module;
-        result = jl_invoke(margs[0], &margs[1], nargs - 1, mfunc);
+        result = jl_apply(margs, nargs);
     }
     JL_CATCH {
         if ((jl_loaderror_type == NULL) || !throw_load_error) {