sqlite build flags: missing usleep support

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

Due to http://code.google.com/p/beets/issues/detail?id=399 I noted
that sqlite3 in NetBSD base doesn't have usleep support, which makes
its backoff algorithm during lock contention back off in whole seconds
instead of microseconds. Which is bad, obviously.

I checked and found the following flags which would be set by
sqlite3's configure automatically and have corresponding ifdefs in the
sqlite3 source:

-DHAVE_INTTYPES_H=1
-DHAVE_STDINT_H=1
-DHAVE_USLEEP=1
-DHAVE_LOCALTIME_R=1
-DHAVE_GMTIME_R=1
-DHAVE_STRERROR_R=1
-DHAVE_READLINE=1

Only two of them, -DHAVE_READLINE=1 -DHAVE_LOCALTIME_R are set by
src/external/public-domain/sqlite/Makefile.inc.

I'd like to add all the other ones. Comments?
 Thomas