doc: clarify which extensions are present in WebGL.

doc/opengl-support.dox

@@ -260,7 +260,7 @@ Extension                                   | Status
 @extension{AMD,vertex_shader_layer}         | done (shading language only)
 @extension{AMD,shader_trinary_minmax}       | done (shading language only)
 @extension{ATI,texture_mirror_once}         | done (GL 4.4 subset)
-@extension{EXT,texture_filter_anisotropic} (also in ES) | done
+@extension{EXT,texture_filter_anisotropic} (also in ES, WebGL) | done
 @extension{EXT,texture_mirror_clamp}        | only GL 4.4 subset
 @extension{EXT,direct_state_access}         | done for implemented functionality
 @extension{EXT,texture_sRGB_decode} (also in ES) | done
@@ -290,15 +290,15 @@ Extension                                   | Status
 ------------------------------------------- | ------
 @es_extension{ANGLE,framebuffer_blit}       | done
 @es_extension{ANGLE,framebuffer_multisample} | done
-@es_extension{ANGLE,instanced_arrays}       | done
+@es_extension{ANGLE,instanced_arrays} (also in WebGL 1.0) | done
 @es_extension{ANGLE,depth_texture}          | done
 @es_extension{APPLE,framebuffer_multisample} | done (ES 3.0 subset)
 @es_extension{APPLE,texture_max_level}      | done
 @es_extension{ARM,rgba8}                    | done
 @es_extension{EXT,texture_type_2_10_10_10_REV} | done
 @es_extension{EXT,discard_framebuffer}      | done
-@es_extension2{EXT,blend_minmax,blend_minmax} | done
-@es_extension{EXT,shader_texture_lod}       | done (shading language only)
+@es_extension2{EXT,blend_minmax,blend_minmax} (also in WebGL 1.0) | done
+@es_extension{EXT,shader_texture_lod} (also in WebGL 1.0) | done (shading language only)
 @es_extension{EXT,occlusion_query_boolean}  | done
 @es_extension{EXT,shadow_samplers}          | done
 @es_extension{EXT,texture_rg}               | done
@@ -317,25 +317,26 @@ Extension                                   | Status
 @es_extension{NV,shadow_samplers_array}     | done (shading language only)
 @es_extension{NV,shadow_samplers_cube}      | done (shading language only)
 @es_extension{OES,depth24}                  | done
-@es_extension{OES,element_index_uint}       | done
+@es_extension{OES,element_index_uint} (also in WebGL 1.0) | done
 @es_extension{OES,rgb8_rgba8}               | done (desktop-compatible subset)
 @es_extension{OES,texture_3D}               | done
-@es_extension2{OES,texture_half_float_linear,OES_texture_float_linear} | done
-@es_extension{OES,texture_float_linear}     | done
-@es_extension2{OES,texture_half_float,OES_texture_float} | done
-@es_extension{OES,texture_float}            | done
+@es_extension2{OES,texture_half_float_linear,OES_texture_float_linear} (also in WebGL 1.0) | done
+@es_extension{OES,texture_float_linear} (also in WebGL 1.0) | done
+@es_extension2{OES,texture_half_float,OES_texture_float} (also in WebGL 1.0) | done
+@es_extension{OES,texture_float} (also in WebGL 1.0) | done
 @es_extension{OES,texture_npot}             | done (nothing to do)
 @es_extension{OES,vertex_half_float}        | done
 @es_extension{OES,packed_depth_stencil}     | done
 @es_extension{OES,depth_texture}            | done
-@es_extension{OES,standard_derivatives}     | done
-@es_extension{OES,vertex_array_object}      | done
+@es_extension{OES,standard_derivatives} (also in WebGL 1,0) | done
+@es_extension{OES,vertex_array_object} (also in WebGL 1.0) | done
 @es_extension{OES,required_internalformat}  | done (desktop-compatible subset)
 @es_extension{OES,surfaceless_context}      | done
 
 @subsection opengl-support-es-extensions OpenGL ES extensions to match desktop functionality
 
-Only extensions not already listed in above tables are included here.
+Only extensions not already listed in above tables (marked with *also in ES*)
+are included here.
 
 @todo @es_extension{NV,non_square_matrices}
 @todo Support also IMG_multisampled_render_to_texture? It has different enum
@@ -376,7 +377,8 @@ supported.
 
 @subsection opengl-support-webgl20-extensions WebGL 1.0 extensions to match WebGL 2.0 functionality
 
-Only extensions not already listed in above tables are included here.
+Only extensions not already listed in above tables (marked with *also in WebGL
+1.0*) are included here.
 
 Extension                                   | Status
 ------------------------------------------- | ------
@@ -385,7 +387,8 @@ Extension                                   | Status
 
 @subsection opengl-support-webgl-extensions WebGL extensions to match desktop functionality
 
-All currently implemented extensions are already listed in above tables.
+All currently implemented extensions are already listed in above tables (marked
+with *also in WebGL*).
 
 @section opengl-unsupported Unsupported OpenGL features