Fix typo in timer normalization constants

The effect of this would be that various update callbacks would
not be made at the correct interval.
Don't report status on named pipes

Git skips entries in directories that are not S_ISDIR, S_ISREG, or
S_ISLNK, so let's make libgit2 do the same thing.
Merge pull request #2506 from libgit2/rb/ignore-pipes-etc

Don't report status on named pipes
Merge pull request #2507 from libgit2/rb/timer-typo

Typo in timer constants