Revert "mesa: Remove pointless comparison of unsigned integer with a negative constant."

This reverts commit a05fdbcb719ac64e6be842372813f0f4ca2f4f93.

Removing the comparison is wrong. The comparison with -1 should be changed
to another value (probably PROGRAM_UNDEFINED) along with another
change in the shader assembler.

Conflicts:

	src/mesa/shader/prog_execute.c
diff --git a/src/mesa/shader/prog_execute.c b/src/mesa/shader/prog_execute.c
index a1c20a3..37750cc 100644
--- a/src/mesa/shader/prog_execute.c
+++ b/src/mesa/shader/prog_execute.c
@@ -1767,10 +1767,15 @@
          break;
       case OPCODE_PRINT:
          {
-            GLfloat a[4];
-            fetch_vector4(&inst->SrcReg[0], machine, a);
-            printf("%s%g, %g, %g, %g\n", (const char *) inst->Data,
-		   a[0], a[1], a[2], a[3]);
+            if (inst->SrcReg[0].File != -1) {
+               GLfloat a[4];
+               fetch_vector4(&inst->SrcReg[0], machine, a);
+               printf("%s%g, %g, %g, %g\n", (const char *) inst->Data,
+                            a[0], a[1], a[2], a[3]);
+            }
+            else {
+               printf("%s\n", (const char *) inst->Data);
+            }
          }
          break;
       case OPCODE_END: