New branch: experimental UDP support
[experimental-udp] initial commit, no support on scl/clisp/armedbear, buggy on others.
[ecl] fix compile by add sys/time.h into includes
[lispworks] fix WAIT-FOR-INPUT on non-win32 platform when TIMEOUT is NIL, by using MP:PROCESS-WAIT.
[experimental-udp] many changes:

 * UDP Proposal change: :tcp/:udp -> :stream/:datagram in PROTOCOL keyword
 * Remove dependency of lispworks-udp, merge necessary code into usocket
[udp] do not import any internal symbol from lispworks COMM
[udp] use :datagram instead of :udp, extend HOST-TO-HBO to support NIL
[udp] add SCL support, untested.
[udp] minor fixes for CMUCL
Merge c428 from trunk: WAIT-FOR-INPUT without timeout (non-Win32).
Merge r418-423: Fix SBCL waiting backend.
Merge c424 from trunk: Stop leaking socket handles.
Change the UNSUPPORTED macro to use CERROR instead of SIGNAL, for REPL users.
Backport c437: Make UNSUPPORTED evaluate to a CERROR, for REPL users.
Report deadline errors as DEADLINE-ERROR instead of TIMEOUT-ERROR
Merge c439: report deadline errors as DEADLINE-ERROR.
[lispworks] on non-win32 platform, add a warn when MP is not enabled when load.
Report more details of a UNKNOWN-ERROR or NS-UNKNOWN-ERROR
Merge c441,442 from branch 0.4.x to trunk
[udp] revert changes to HOST-TO-HOSTNAME and HOST-TO-HBO, just bad idea.