Update docs:

- Some comments in hip_hcc.cpp
 - document hipHostRegister* flags.
 - expand docs on hipHostRegister/Unregister. Use "register" rather than
   "pin" to describe action these take.
 - change required CUDA version to 6 (require unified memory)
 - remake doxygen.

docs/RuntimeAPI/html/search/all_6.js

@@ -1,4 +1,4 @@
 var searchData=
 [
-  ['global_20enum_20and_20defines',['Global enum and defines',['../group__GlobalDefs.html',1,'']]]
+  ['fakemutex',['FakeMutex',['../classFakeMutex.html',1,'']]]
 ];