mesa: change ctx->Driver.ProgramStringNotify() to return GLboolean

GL_TRUE indicates that the driver accepts the program.
GL_FALSE indicates the program can't be compiled/translated by the
driver for some reason (too many resources used, etc).

Propogate this result up to the GL API: set GL_INVALID_OPERATION
error if glProgramString() was called.  Set shader program link
status to GL_FALSE if glLinkProgram() was called.

At this point, drivers still don't do any program checking and
always return GL_TRUE.
diff --git a/src/mesa/main/texenvprogram.c b/src/mesa/main/texenvprogram.c
index 499b733..414607e 100644
--- a/src/mesa/main/texenvprogram.c
+++ b/src/mesa/main/texenvprogram.c
@@ -1535,8 +1535,15 @@
    /* Notify driver the fragment program has (actually) changed.
     */
    if (ctx->Driver.ProgramStringNotify) {
-      ctx->Driver.ProgramStringNotify( ctx, GL_FRAGMENT_PROGRAM_ARB, 
-                                       &p.program->Base );
+      GLboolean ok = ctx->Driver.ProgramStringNotify(ctx,
+                                                     GL_FRAGMENT_PROGRAM_ARB, 
+                                                     &p.program->Base);
+      /* Driver should be able to handle any texenv programs as long as
+       * the driver correctly reported max number of texture units correctly,
+       * etc.
+       */
+      ASSERT(ok);
+      (void) ok; /* silence unused var warning */
    }
 
    if (DISASSEM) {