- fix an error in the SCR calculation that would cause an extra frame to be dropped...

 - fix an error in the SCR calculation that would cause an extra frame to be dropped at an SCR discontinuity.
 - fix a rounding error in the encx264 init_delay computation that would underestimate the delay for progressive content and cause spurious "init_delay too small" messages.
 - clean up the sync.c "video time didn't advance" logic and try to make the error mgs more useful for debugging frame duration problems.

git-svn-id: svn://localhost/HandBrake/trunk@1543 b64f7644-9d1e-0410-96f1-a4d463321fa5