* Windows DLL-Load-Errors
Added error reporting using formatmessage, ignoring if the DLL just
doesn't exist, custom warning for "[193 (0xC1)] is not a valid Win32
application." (probably wrong architecture)
* update gitignore with build folder
handling SIGTTIN/OU allows running Doom3 in the background (or even
sending it to the background with Ctrl-Z + bg) by disabling TTY input
(before it would get stuck when run in background without +set in_tty 0,
see #215)
While at it, I also added signal handlers for some common crash signals
(SIGILL, SIGABRT, SIGFPE, SIGSEGV) to print a backtrace before exiting
the game (partly based on Yamagi Quake II code).
Let scons link directly in the build folder.
Multiple archs can coexist next to each other.
New scons variable "X86" to cross compile x86 binaries on x86_64.
