Fix #254 - no more crashes when calling Com_Error!

Problem was that the game library calling Com_Error was then being unloaded by Com_Error. I had checked this before but obviously not with enough detail. The libraries are now unloaded using a 'delayed free' feature where the libraries are not actually unloaded until after the exception has been caught.
Fix crash in SP when enabling EAX in Linux/Mac

This is the same fix as in 644e5ca for MP.
Updated readme file

Reworded a lot of the text, and updated some of the information. Also made the forum link easier to see.
Fix Com_Error for SP (similar to fix in 5c4285a)
Fix for last commit - forgot about Windows!
Fix #317: in_joystickThreshold was not initialised
Fix out of bounds access when loading CTF/CTY
Fix game library unloading when calling Com_Error.
Fixing MSVC projects additional include directories and common renderer files
Optimised RotatePointAroundVector from q3mme
Fix missing const qualifier on VectorRotate
Refactored renderer API, fixed some Ghoul2 crashes
Fixing previous commit for SDL backend
Merge ioquake/ioq3@943d94b
Use GENTITYNUM_BITS for jumppad_ent bits.
Missing name in clientdisconnect log printf, whoops.