PR bootstrap/19818: fix libcpp warnings

[Paolo Bonzini]

> I don't see why you added getopt and basename to the AC_CHECK_DECLS
> list.  It's lbasename and getopt_long that are used, and the macros
> that you defined are not referenced anywhere.

They are used in libiberty.h and getopt.h respectively.  You have to add 
the AC_CHECK_DECLS otherwise they are declared as K&R function 
declarations and you get a "missing prototype" warning.

> Please run the gengtype changes by Geoff Keating.

CCed now.

Paolo