Promote libevent to lib/ level and fold ftp-proxy into its parent Makefile.
This allows us to use libevent for other application in the future.

For now libevent is still INTERNALLIB and no shared library is installed.

MFC after:	1 month
Import patch from libc++ r197313 which allows using libc++ headers with gcc

Differential Revision:	https://reviews.freebsd.org/D942
Reviewed by:	imp
Fix awk(1) asorti() implementation to work when called in a loop.

MFC after:	3 days
X-MFC-to:	stable/10, stable/9
Rename awk(1) implementation of GNU awk's built-in asorti() function to
prevent fatal conflict should one-true-awk ever be replaced -- e.g., in
an appliance -- with GNU awk. NB: Renamed my implementation to _asorti()

MFC after:	3 days
X-MFC-to:	stable/10, stable/9