getpass misplaced

[Isaac Dunham <idunham@lavabit.com>]

I know getpass is an atrocious security mistake of years ago, but
if we are going to support it, glibc defines it with GNU, BSD, or *old*
X/Open feature macros in <unistd.h>, not <pwd.h>.

Also, I've found two more headers that actually don't need _BSD_SOURCE
added before they offer the BSD functionality (all BSD functions are
also available in every other relevant namespace): pwd.h and utmp.h.

This has me down to 22 headers that still need work/reviewing. Here's
the TODO for _BSD_SOURCE:

include/tgmath.h
include/glob.h
include/arpa/inet.h
include/sys/select.h
include/sys/wait.h
include/sys/socket.h
include/sys/un.h
include/sys/uio.h
include/sys/mman.h
include/sys/stat.h
include/setjmp.h
include/dirent.h
include/time.h
include/netinet/ip.h
include/netinet/tcp.h
include/netinet/ip_icmp.h
include/netinet/in.h		Missing structs
include/netinet/if_ether.h
include/shadow.h
include/endian.h
include/grp.h
include/net/if.h

<netinet/in.h> could cause breakage without extension.  I forget
exactly what the problem was, though.
Isaac Dunham