support for HDMI standby and (de)activation, override autodetected HDMI port, better support for Samsung TV, etc...

Hi,

I'm not sure if you are still working on this project, but here's my contribution. I tried to finish the few loose end, fix a few bugs here and there, and added the few features which make my MythTV setup great with libcec-daemon.

Cheers,
   Damien

Changes summary:

- main.cpp, libcec.cpp: added support for HDMI port overrides in case autodetection fails (libcec detection doesn't work with proprietary NVIDIA driver)
- main.cpp, libcec.cpp: added support for custom events such CEC-standby, CEC-activate, CEC-deactivate via custom scripts
- main.cpp, libcec.cpp: support for adapter recovery after plug/unplug (after a resume or thaw) by reinitalizing adapter after ping failure.
- main.cpp, libcec.cpp: finish support for multiple usb adapter, only shim code was available previously
- main.cpp, uinput.cpp: support for CEC combo keycode such as UP-LEFT, DOWN-RIGHT by issuing multiple keypresses together
- main.cpp: simulate relevant keypress/keyrelease if they are not properly sent by TV remote, such as old Samsung TV or some vendor code.
- main.cpp, hdmi.cpp: improve command line arguments help and parsing for HDMI port address
- bootstrap, configure.ac, m4, Makefile.am: support for autoconf/automake build in order to help integrating with distros package managers