Let player prehear sound settings in options screen

.. rather than the current set volumes then click ok to hear the
difference repeat until satisfied approach.
Fix build on Ubuntu since yaml-cpp 0.5 upgrade.

Thanks to sjamaan for help on #OpenXcom, and this Stack Overflow question for the solution: http://stackoverflow.com/questions/3128497/compiler-error-coming-out-of-yaml-cpp
Merge pull request #641 from cfailde/prehear

Let player prehear sound settings in options screen
Merge pull request #642 from evktalo/master

Fix build on Ubuntu since yaml-cpp 0.5 upgrade.
Fix units being saved from zombification by player saving game

as currently the necessary information is not being recorded in the save
file
Merge pull request #643 from cfailde/zombie_fix

Fix units being saved from zombification by player saving game
Experimental options cause UI issues? Naaaaaaah
Debug coordinates