* Timer HAL module
* Refactored code from i_system.cpp into i_sdltimer.cpp
* Eliminated I_WaitVBL

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2840 86ba831e-150c-0410-ab35-e06eaae15ed9
Revamped interpolation; hopefully more tolerant of timing variances (similar to PrBoom-plus and D64EX)

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2841 86ba831e-150c-0410-ab35-e06eaae15ed9