add 'tail' capability to 'attach_mail_file' function, shortened 'alloy_build_log.log' being sent to 100 lines in case of success and 400 in case of failure
removed a bug
Merge pull request #820 from ncos/ispc-mail-tail

This will make 'alloy_build' shorter
Moving 3.4 build to LLVM 3.4.2 release.
Merge pull request #822 from dbabokin/dot2

Moving 3.4 build to LLVM 3.4.2 release.