fix for tinderbox

>vcl/inc/opengl/TextureState.hxx:28:10:
> error: this method can be declared static TextureState::generate
> [loplugin:staticmethods]
>vcl/inc/opengl/RenderState.hxx:22:10:
> error: this method can be declared static GenericCapabilityState::readState
> [loplugin:staticmethods]
>vcl/inc/opengl/RenderState.hxx:24:17:
> error: implicit conversion (IntegralCast) from 'GLboolean'
> (aka 'unsigned char') to 'int'
> [loplugin:implicitboolconversion]

Change-Id: Iafcfe6c88b7e570d7c73a9e8920fdd7c6248ad7b
Reviewed-on: https://gerrit.libreoffice.org/24541Reviewed-by: Jochen Nitschke <j.nitschke+logerrit@ok.de>
Tested-by: Jochen Nitschke <j.nitschke+logerrit@ok.de>

vcl/inc/opengl/RenderState.hxx

@@ -19,10 +19,10 @@ class GenericCapabilityState
 protected:
     bool mbTest;
 
-    bool readState()
+    static bool readState()
     {
-        return (glIsEnabled(ENUM_TYPE) == GL_TRUE);
-    };
+        return (glIsEnabled(ENUM_TYPE) == static_cast<GLboolean>(GL_TRUE));
+    }
 
 public:
     void sync()

vcl/inc/opengl/TextureState.hxx

@@ -25,7 +25,7 @@ public:
         , maBoundTextures(4, 0)
     {}
 
-    void generate(GLuint& nTexture)
+    static void generate(GLuint& nTexture)
     {
         glGenTextures(1, &nTexture);
         CHECK_GL_ERROR();