[evas_gl_thread] Refactoring evas gl thread

[evas_gl_thread]  Refactoring evas gl thread
1. combine the gl and evgl threads together
   : export EVAS_GL_RENDER_THREAD=1
2. Changed the pushing method of thread commands

    Now user can allocate a command buffer first, then enqueue it.
    It will be free automatically after callback is called.

    GL_TH_ST(command) *buf;
    void *thcmd_ref;
    buf = evas_gl_thread_cmd_create(EVAS_GL_THREAD_TYPE_GL,
                                    sizeof(GL_TH_ST(command)),
                                    &thcmd_ref);
    buf->xxx = xxxx; // Setup content
    evas_gl_thread_cmd_enqueue(thcmd_ref
                               GL_TH_CB(command),
                               EVAS_GL_THREAD_MODE_FINISH);
3. Refactoring Thread functions of EGL/GLX to the new form
4. Replace GL_TH and EVGL_TH to the new form
5. Refactoring EvasGL macro to attach thread funcs
6. Replace dlopen'ed symbols (glsym_XXX)
7. Replace functional threading codes to the new form
8. Enable direct rendering when evas gl thread is On

Change-Id: Ie88edd77f670b59ac5fae8ce9c34753c2bd36009