Update Compatibility section

OS X has been supported since 0.34.11r3
Installation instructions for Homebrew
Add paths for Homebrew's gcc and g++
Add missing import/export info for MersenneRNG::unitvector<>
Fix siege-engine to compile on Windows - don't have C++11, and pow() is picky about arg types
Update to Lua 5.2.3
Reapply dfhack-specific lua build configuration.
Rename the LUA_PATH/LUA_CPATH environment variables to avoid conflicts.

If a user has a standalone lua installation with these variables
configured, it should not confuse dfhack into looking for things
in wrong places.
Merge branch 'lua-5.2.3' into develop
Support using multiple lua init scripts per save.

This should make it easier to add and remove init script code by
automated means, or install multiple mods that need such code.
ruby: use placement-new instead of hack
Fix a mistake in the lua resize() method of BitArray.
Update structures and fix broken things.
Merge a mod-manager fix from 'warmist/develop' into develop
Merge OSX build docs from git://github.com/lethosor/dfhack into develop
Generate html files.
Update the structures.
Update XML, fix several scripts that were broken by field name changes
Fix some signed/unsigned mismatch warnings and whitespace in Job module.
Add new API functions for creating announcements and combat reports.

Allow specifying the announcement flags directly, and adding unit
combat reports. Also, make announcement functions write the message
to the game log.