Don't export nonexistent functions

Caught by an aimake upgrade.
Work around a bug in some glibc versions

-D_XOPEN_SOURCE=700 should be enough, the _POSIX_C_SOURCE definition
is redundnat. However, some systems seem to need it in practice to
provide siginfo_t.
Update aimake to version 3.1

This should fix compile failures for many people.
Merge remote-tracking branch 'dtsund/savebreak' into savebreak

Conflicts:
	libnethack/src/do_wear.c
	libnethack/src/pickup.c
Add Jonadab the Unsightly One to the credits
Merge remote-tracking branch 'dtsund/savebreak' into savebreak

Conflicts:
	libnethack/src/do_wear.c
	libnethack/src/pickup.c