Integrate Global "from" option; reorganize code

Integrate Global "from" option; reorganize code

 * src/global.c: Integrate SF.net patch #1211520 (from bruder2k) with a small
   bug fix; this patch adds a "from" option to Global notices and messages.

 * src/global.c, src/global.h: Make struct globalMessage private; cache text
   form of message's post date/time to avoid repeated strftime() calls.
git-archimport-id: srvx@srvx.net--2005-srvx/srvx--devo--1.3--patch-22