mesa: expose support for GL_EXT_buffer_storage

This extension requires ES 3.1 since it relies on glMemoryBarrier.
For testing purposes I temporarily moved glMemoryBarrier to be an ES 3.0
function.
This has been tested with the piglit in the ML and the Dolphin emulator.

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

docs/relnotes/11.1.0.html

@@ -56,6 +56,7 @@ Note: some of the new features are only available with certain drivers.
 <li>GL_ARB_texture_barrier / GL_NV_texture_barrier on i965</li>
 <li>GL_ARB_texture_query_lod on softpipe</li>
 <li>GL_ARB_texture_view on radeonsi</li>
+<li>GL_EXT_buffer_storage implemented for when ES 3.1 support is gained</li>
 <li>GL_EXT_draw_elements_base_vertex on all drivers</li>
 <li>GL_OES_draw_elements_base_vertex on all drivers</li>
 <li>EGL_KHR_create_context on softpipe, llvmpipe</li>

src/mapi/glapi/gen/es_EXT.xml

@@ -905,4 +905,13 @@
 
 </category>
 
+<category name="GL_EXT_buffer_storage" number="239">
+    <function name="BufferStorageEXT" alias="BufferStorage" es2="3.1">
+        <param name="target" type="GLenum"/>
+        <param name="size" type="GLsizeiptr"/>
+        <param name="data" type="const GLvoid *"/>
+        <param name="flags" type="GLbitfield"/>
+    </function>
+</category>
+
 </OpenGLAPI>

src/mesa/main/extensions.c

@@ -222,6 +222,7 @@ static const struct extension extension_table[] = {
    { "GL_EXT_blend_color",                         o(EXT_blend_color),                         GLL,            1995 },
    { "GL_EXT_blend_equation_separate",             o(EXT_blend_equation_separate),             GL,             2003 },
    { "GL_EXT_blend_func_separate",                 o(EXT_blend_func_separate),                 GLL,            1999 },
+   { "GL_EXT_buffer_storage",                      o(ARB_buffer_storage),                                 ES31, 2015 },
    { "GL_EXT_discard_framebuffer",                 o(dummy_true),                                    ES1 | ES2, 2009 },
    { "GL_EXT_blend_minmax",                        o(EXT_blend_minmax),                        GLL | ES1 | ES2, 1995 },
    { "GL_EXT_blend_subtract",                      o(dummy_true),                              GLL,            1995 },