mesa: support boolean and integer-based parameters in prog_parameter

The functionality is not used by anything yet, and the glUniform functions will
need to be reworked before this can reach its full usefulness.  It is
nonetheless a step towards integer support in the state tracker and classic drivers.
diff --git a/src/mesa/program/program.c b/src/mesa/program/program.c
index 224446a..4f2b627 100644
--- a/src/mesa/program/program.c
+++ b/src/mesa/program/program.c
@@ -1030,7 +1030,8 @@
    GLuint i;
    GLuint whiteSwizzle;
    GLint whiteIndex = _mesa_add_unnamed_constant(prog->Parameters,
-                                                 white, 4, &whiteSwizzle);
+                                                 (gl_constant_value *) white,
+                                                 4, &whiteSwizzle);
 
    (void) whiteIndex;