mesa: new _NEW_PROGRAM_CONSTANTS flag

This state flag will be used to indicate that vertex/fragment program
constants have changed.  _NEW_PROGRAM will be used to indicate changes
to the vertex/fragment shader itself, or misc related state.

_NEW_PROGRAM_CONSTANTS is also set whenever a program parameter that's
tracking GL state has changed.  For example, if the projection matrix is
in the parameter list, calling glFrustum() will cause _NEW_PROGRAM_CONSTANTS
to be set.  This will let to remove the need for dynamic state atoms in
some drivers.

For now, we still set _NEW_PROGRAM in all the places we used to.  We'll no
longer set _NEW_PROGRAM in glUniform() after drivers/etc have been updated.
diff --git a/src/mesa/shader/shader_api.c b/src/mesa/shader/shader_api.c
index 9038f7d..644cd39 100644
--- a/src/mesa/shader/shader_api.c
+++ b/src/mesa/shader/shader_api.c
@@ -1789,7 +1789,7 @@
       return;
    }
 
-   FLUSH_VERTICES(ctx, _NEW_PROGRAM);
+   FLUSH_VERTICES(ctx, _NEW_PROGRAM | _NEW_PROGRAM_CONSTANTS);
 
    uniform = &shProg->Uniforms->Uniforms[location];
 
@@ -1929,7 +1929,7 @@
       return;
    }
 
-   FLUSH_VERTICES(ctx, _NEW_PROGRAM);
+   FLUSH_VERTICES(ctx, _NEW_PROGRAM | _NEW_PROGRAM_CONSTANTS);
 
    uniform = &shProg->Uniforms->Uniforms[location];