-Wall -Wno-unused-param

[Eli Zaretskii]

   With regard to ATTRIBUTE_UNUSED, GDB is sitting at a cross road where
   people could either go through and add that everywhere or just require
   people to use a state-of-the-art compiler to check for warnings.  I like
   the latter, its easier overall :-)

For reasons I'd pefer not to go into here, I (still) don't trust GCC
2.95.x enough to rely on the latest version of the compiler.

I've already changed go32-nat.c and ser-go32.c to use ATTRIBUTE_UNUSED
so as to shut up the compiler.  YMMV.