Added some more functions to knc.h:
- __scatter64_i64
- __scatter_base_offsets32_double
- __scatter_base_offsets32_i64
- fixed 'cast_trunc', 'cast_zext' and 'cast_sext' implementations (the previous was faulty)
- added '__select (i8/16)', '__equal_i8/16_and_mask', '__not_equal_i8/16_and_mask' functions
Merge branch 'master' of https://github.com/ncos/ispc into knc-backend-merge

Conflicts:
	examples/intrinsics/knc.h
removed unnecessary &255's (knc.h)
updated fail_db.txt to hide 9 new runfails and tests that have been fixed
Merge pull request #903 from ncos/knc-backend-merge

Add several functions to knc.h