spirv_extensions: add GL_ARB_spirv_extensions boilerplate

v2:
  * Mention extension gap at gl_API.xml (Emil Velikov)
  * Bail with INVALID_ENUM if extension not available on getStringi (Emil Velikov)
  * Use EXTRA_EXT macro when defining the extension at
    get.c/get_hash_params.py (Emil Velikov)
  * Rename source files (spirvextensions.[ch] -> spirv_extensions.[ch]) (Ian)

v3:
  * Fix GL_PROGRAM_BINARY_FORMATS glGet query, broken by error on a
    previous rebase

v4:
   * Fix rebase conflicts on getstring.c after
     GL_SHADING_LANGUAGE_VERSION query was added

v5:
   * Remove src/mapi/glapi/gen/Makefile.am as it no longer exists in
     master

Signed-off-by: Alejandro Piñeiro <apinheiro@igalia.com>
Signed-off-by: Arcady Goldmints-Orlov <agoldmints@igalia.com>

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

src/mapi/glapi/gen/ARB_spirv_extensions.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0"?>
+<!DOCTYPE OpenGLAPI SYSTEM "gl_API.dtd">
+
+<OpenGLAPI>
+
+<category name="GL_ARB_spirv_extensions" number="194">
+
+    <enum name="SPIR_V_EXTENSIONS" value="0x9553"/>
+    <enum name="NUM_SPIR_V_EXTENSIONS" value="0x9554"/>
+
+</category>
+
+</OpenGLAPI>

src/mapi/glapi/gen/gl_API.xml

@@ -8424,6 +8424,10 @@
 
 <xi:include href="ARB_gl_spirv.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
 
+<!-- ARB extensions 191 - 193 -->
+
+<xi:include href="ARB_spirv_extensions.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
+
 <!-- Non-ARB extensions sorted by extension number. -->
 
 <category name="GL_EXT_blend_color" number="2">

src/mapi/glapi/gen/meson.build

@@ -82,6 +82,7 @@ api_xml_files = files(
   'ARB_shader_subroutine.xml',
   'ARB_shader_storage_buffer_object.xml',
   'ARB_sparse_buffer.xml',
+  'ARB_spirv_extensions.xml',
   'ARB_sync.xml',
   'ARB_tessellation_shader.xml',
   'ARB_texture_barrier.xml',