Revert "tetris: part 1 of fixing building it with v2"

This reverts commit d42725aafe.

vlib/gl/gl.v

@@ -11,8 +11,6 @@ module gl
 // joe-c: fix & remove
 pub enum TmpGlImportHack{ non_empty }
 
-fn C.gladLoadGL() int
-
 fn C.glDisable()
 fn C.glEnable()
 fn C.glScissor()
@@ -46,6 +44,7 @@ fn C.glClear()
 fn C.glCreateShader() int
 fn C.glClearColor()
 fn C.glViewport()
+fn C.gladLoadGL()
 fn C.glTexImage2D()
 fn C.glPixelStorei()
 fn C.glBlendFunc()
@@ -53,9 +52,10 @@ fn C.glPolygonMode()
 fn C.glDeleteBuffers()
 
 
+
 pub fn init_glad() {
 	ok := C.gladLoadGL()
-	if ok == 0 {
+	if isnil(ok) {
 		println('Failed to initialize glad OpenGL context')
 		exit(1)
 	}