compiler, runtime: add layout parameter to runtime.alloc

This layout parameter is currently always nil and ignored, but will
eventually contain a pointer to a memory layout.

This commit also adds module verification to the transform tests, as I
found out that it didn't (and therefore didn't initially catch all
bugs).

src/runtime/arch_tinygowasm.go

@@ -66,7 +66,7 @@ func growHeap() bool {
 
 //export malloc
 func libc_malloc(size uintptr) unsafe.Pointer {
-	return alloc(size)
+	return alloc(size, nil)
 }
 
 //export free
@@ -79,7 +79,7 @@ func libc_calloc(nmemb, size uintptr) unsafe.Pointer {
 	// Note: we could be even more correct here and check that nmemb * size
 	// doesn't overflow. However the current implementation should normally work
 	// fine.
-	return alloc(nmemb * size)
+	return alloc(nmemb*size, nil)
 }
 
 //export realloc