Bug with -fsyntax-only

[Anthony Jackson]

Running gcc 2.95.2 on alphaev56-dec-osf4.0d, the -fsyntax-only flag does
not work properly; it always generates an error on any .c file, because
it attempts to run as with a null input file.

This can be fixed by adding the -S flag to the command line, but the
documentation does not specify that this is necessary, and it should not
really be required.

This can be demonstrated by running gcc -fsyntax-only on any .c file; a
"hello world" program works fine.