In _mesa_add_unnamed_constant() and _mesa_lookup_parameter_constant() allow swizzleOut==NULL.

There are times when we don't want to allow swizzling when searching for or
adding vector constants.  Passing NULL for swizzleOut disables swizzling.
This fixes a constant/swizzle bug in link_uniform_vars().
diff --git a/src/mesa/shader/nvfragparse.c b/src/mesa/shader/nvfragparse.c
index b4e19ce..c46d8aa 100644
--- a/src/mesa/shader/nvfragparse.c
+++ b/src/mesa/shader/nvfragparse.c
@@ -1040,7 +1040,7 @@
       if (!Parse_ScalarConstant(parseState, values))
          RETURN_ERROR;
       paramIndex = _mesa_add_unnamed_constant(parseState->parameters,
-                                              values, 4, &swizzle);
+                                              values, 4, NULL);
       ASSERT(swizzle == SWIZZLE_NOOP);
       srcReg->File = PROGRAM_NAMED_PARAM;
       srcReg->Index = paramIndex;
@@ -1053,7 +1053,7 @@
       if (!Parse_VectorConstant(parseState, values))
          RETURN_ERROR;
       paramIndex = _mesa_add_unnamed_constant(parseState->parameters,
-                                              values, 4, &swizzle);
+                                              values, 4, NULL);
       ASSERT(swizzle == SWIZZLE_NOOP);
       srcReg->File = PROGRAM_NAMED_PARAM;
       srcReg->Index = paramIndex;      
@@ -1145,7 +1145,7 @@
       if (!Parse_VectorConstant(parseState, values))
          RETURN_ERROR;
       paramIndex = _mesa_add_unnamed_constant(parseState->parameters,
-                                              values, 4, &swizzle);
+                                              values, 4, NULL);
       ASSERT(swizzle == SWIZZLE_NOOP);
       srcReg->File = PROGRAM_NAMED_PARAM;
       srcReg->Index = paramIndex;      
@@ -1171,7 +1171,7 @@
       if (!Parse_ScalarConstant(parseState, values))
          RETURN_ERROR;
       paramIndex = _mesa_add_unnamed_constant(parseState->parameters,
-                                              values, 4, &swizzle);
+                                              values, 4, NULL);
       ASSERT(swizzle == SWIZZLE_NOOP);
       srcReg->Index = paramIndex;      
       srcReg->File = PROGRAM_NAMED_PARAM;