[x265] patch for faster intra

[dave]

I am submitting a patch to implement the faster intra search suggested 
by Steve Borho here:

https://mailman.videolan.org/pipermail/x265-devel/2014-July/004873.html

The patch is implements the faster search in slicetype.cpp.  The same 
approach can also be used in analysis.cpp but it's a little more than a 
simple cut and paste though it shouldn't take long.

TEncSearch.cpp also calls intra_pred_allangs for which this is the 
faster alternative but at first look, TEncSearch.cpp is more complex.  
Depending on what is desired, either this search could greatly simplify 
this part of TEncSearch.cpp or it might not be applicable to what 
TEncSearch.cpp is doing.  I will be looking into it.

Dave