mesa: Add types for AMD_depth_clamp_separate.

Add some basic types and storage for the AMD_depth_clamp_separate
extension.

v2: 1) Drop unnecessary definition (Marek Olsak)
    2) Expose extension in compatibility profile (Marek Olsak)

Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/mesa/main/extensions_table.h

@@ -9,6 +9,7 @@
 EXT(3DFX_texture_compression_FXT1           , TDFX_texture_compression_FXT1          , GLL, GLC,  x ,  x , 1999)
 
 EXT(AMD_conservative_depth                  , ARB_conservative_depth                 , GLL, GLC,  x ,  x , 2009)
+EXT(AMD_depth_clamp_separate                , AMD_depth_clamp_separate               , GLL, GLC,  x ,  x , 2009)
 EXT(AMD_draw_buffers_blend                  , ARB_draw_buffers_blend                 , GLL, GLC,  x ,  x , 2009)
 EXT(AMD_framebuffer_multisample_advanced    , AMD_framebuffer_multisample_advanced   , GLL, GLC,  x , ES2, 2018)
 EXT(AMD_gpu_shader_int64                    , ARB_gpu_shader_int64                   ,  x , GLC,  x ,  x , 2015)

src/mesa/main/mtypes.h

@@ -1283,6 +1283,8 @@ struct gl_transform_attrib
    GLboolean RescaleNormals;			/**< GL_EXT_rescale_normal */
    GLboolean RasterPositionUnclipped;           /**< GL_IBM_rasterpos_clip */
    GLboolean DepthClamp;			/**< GL_ARB_depth_clamp */
+   GLboolean DepthClampNear;			/**< GL_AMD_depth_clamp_separate */
+   GLboolean DepthClampFar;			/**< GL_AMD_depth_clamp_separate */
    /** GL_ARB_clip_control */
    GLenum16 ClipOrigin;   /**< GL_LOWER_LEFT or GL_UPPER_LEFT */
    GLenum16 ClipDepthMode;/**< GL_NEGATIVE_ONE_TO_ONE or GL_ZERO_TO_ONE */
@@ -4257,6 +4259,7 @@ struct gl_extensions
    GLboolean OES_viewport_array;
    /* vendor extensions */
    GLboolean AMD_framebuffer_multisample_advanced;
+   GLboolean AMD_depth_clamp_separate;
    GLboolean AMD_performance_monitor;
    GLboolean AMD_pinned_memory;
    GLboolean AMD_seamless_cubemap_per_texture;