ptr-22 test fixed on knc. removing from fail_db.txt
12 runfails tracked in #20472 (LLVM trunk commit 213898 by Chandler)
llvm 3.6 generic-4/16 compfails (already added for llvm 3.5)
Merge pull request #847 from ncos/knc_faildb

Modifications of fail_db.txt: ptr-22 fixed; runfails #20472; generic compfails 3.5->3.6