Remove cp_error040.c: The error message is correct, though not necessary (gcc 4.2...

Remove cp_error040.c: The error message is correct, though not necessary (gcc 4.2.3 does not compile Quakeforge 0.5.5 either).  §6.2.2 clause 7: "If, within a translation unit, the same identifier appears with both internal and external linkage, the behavior is undefined.".

[r20982]