mesa: add GLSLVersionCompat constant

This allows drivers to define what version of GLSL they support
in compat. This will be needed in order to support compat 3.2
without breaking drivers that wont support it.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/mesa/drivers/dri/i915/intel_extensions.c

@@ -78,6 +78,7 @@ intelInitExtensions(struct gl_context *ctx)
    ctx->Extensions.OES_draw_texture = true;
 
    ctx->Const.GLSLVersion = 120;
+   ctx->Const.GLSLVersionCompat = 120;
    _mesa_override_glsl_version(&ctx->Const);
 
    if (intel->gen >= 3) {

src/mesa/drivers/dri/i965/intel_extensions.c

@@ -148,6 +148,12 @@ intelInitExtensions(struct gl_context *ctx)
       ctx->Const.GLSLVersion = 330;
    else
       ctx->Const.GLSLVersion = 120;
+
+   if (devinfo->gen >= 6)
+      ctx->Const.GLSLVersionCompat = 130;
+   else
+      ctx->Const.GLSLVersionCompat = 120;
+
    _mesa_override_glsl_version(&ctx->Const);
 
    ctx->Extensions.EXT_shader_integer_mix = ctx->Const.GLSLVersion >= 130;

src/mesa/main/mtypes.h

@@ -3649,6 +3649,7 @@ struct gl_constants
    GLuint MaxGeometryTotalOutputComponents;
 
    GLuint GLSLVersion;  /**< Desktop GLSL version supported (ex: 120 = 1.20) */
+   GLuint GLSLVersionCompat;  /**< Desktop compat GLSL version supported  */
 
    /**
     * Changes default GLSL extension behavior from "error" to "warn".  It's out

src/mesa/main/version.c

@@ -588,9 +588,7 @@ _mesa_get_version(const struct gl_extensions *extensions,
       /* Disable higher GLSL versions for legacy contexts.
        * This disallows creation of higher compatibility contexts. */
       if (!consts->AllowHigherCompatVersion) {
-         if (consts->GLSLVersion > 140) {
-            consts->GLSLVersion = 140;
-         }
+         consts->GLSLVersion = consts->GLSLVersionCompat;
       }
       /* fall through */
    case API_OPENGL_CORE:

src/mesa/state_tracker/st_extensions.c

@@ -936,6 +936,7 @@ void st_init_extensions(struct pipe_screen *screen,
 
    /* Figure out GLSL support and set GLSLVersion to it. */
    consts->GLSLVersion = screen->get_param(screen, PIPE_CAP_GLSL_FEATURE_LEVEL);
+   consts->GLSLVersionCompat = 140;
 
    _mesa_override_glsl_version(consts);