mesa shaderapi: don't enable various functions for GL CORE

These EXT_separate_shader_objects function will no longer be
enabled for CORE profiles:
* UseShaderProgramEXT
* ActiveProgramEXT
* CreateShaderProgramEXT

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

src/mesa/main/shaderapi.c

 
    if (_mesa_is_desktop_gl(ctx)) {
       SET_ProgramParameteriARB(exec, _mesa_ProgramParameteriARB);
+   }
 
+   if (ctx->API == API_OPENGL) {
       SET_UseShaderProgramEXT(exec, _mesa_UseShaderProgramEXT);
       SET_ActiveProgramEXT(exec, _mesa_ActiveProgramEXT);
       SET_CreateShaderProgramEXT(exec, _mesa_CreateShaderProgramEXT);