wined3d: Bind correct number of samplers for GLSL shaders.

We are only checking against GL_MAX_TEXTURES when binding samplers,
when we should be checking against the maximum number of samplers that
the card supports.  Spotted by H. Verbeet.

dlls/wined3d/glsl_shader.c

@@ -60,7 +60,7 @@ void shader_glsl_load_psamplers(
     int i;
     char sampler_name[20];
 
-    for (i=0; i< GL_LIMITS(textures); ++i) {
+    for (i=0; i< GL_LIMITS(samplers); ++i) {
         if (stateBlock->textures[i] != NULL) {
            snprintf(sampler_name, sizeof(sampler_name), "Psampler%d", i);
            name_loc = GL_EXTCALL(glGetUniformLocationARB(programId, sampler_name));