opengl: Remove compiler warnings.

Simply remove multiple compiler warnings about unused parameter.
Note that this modifies three auto-generated files, which will
require fixing the 'emugen' program in the future.

Change-Id: I19edce7c6480770b893d033ed6b1c65744091d62
diff --git a/system/GLESv2_enc/GL2Encoder.cpp b/system/GLESv2_enc/GL2Encoder.cpp
index 3b2100e..9490571 100644
--- a/system/GLESv2_enc/GL2Encoder.cpp
+++ b/system/GLESv2_enc/GL2Encoder.cpp
@@ -150,6 +150,8 @@
 
 const GLubyte *GL2Encoder::s_glGetString(void *self, GLenum name)
 {
+    (void)self;
+
     GLubyte *retval =  (GLubyte *) "";
     switch(name) {
     case GL_VENDOR:
@@ -403,6 +405,8 @@
     GL2Encoder *ctx = (GL2Encoder *)self;
     if (ctx->m_state == NULL) return;
 
+    (void)pname;
+
     const GLClientState::VertexAttribState *va_state = ctx->m_state->getState(index);
     if (va_state != NULL) {
         *pointer = va_state->data;