[r300] fix glxinfo

[Rune Petersen]

Hi,
Using exit() on single buffer is not friendly with glxinfo.
glxinfo exits before it gives any info.
Rune Petersen
diff -Naur b/r300/r300_context.c a/r300/r300_context.c
--- b/r300/r300_context.c       2005-02-12 00:36:43.000000000 +0100
+++ a/r300/r300_context.c       2005-02-12 00:39:16.000000000 +0100
@@ -219,7 +219,8 @@
        ctx = r300->radeon.glCtx;
        if(ctx->Visual.doubleBufferMode == 0){
                fprintf(stderr, "Help me! Single buffer mode doesnt work 
yet.\n");
-               exit(-1);
+               FREE(r300);
+               return GL_FALSE;
        }
        ctx->Const.MaxTextureImageUnits = 
driQueryOptioni(&r300->radeon.optionCache,
                                                     "texture_image_units");