Proposal: better timestamp granularity for modificationTime/setFileTimes in System.Posix.Files[.ByteString]

[Marios Titas]

Dear all,

System.Posix.Files[.ByteString] contains the following functions
related to file times: accessTime, modificationTime, statusChangeTime,
setFileTimes.
All of these functions offer granularity of one second. Modern posix
systems support newer functions (such as utimes, utimensat) that offer
better granularity (up to 1 nanosecond).
I propose to add a new set of functions to
System.Posix.Files[.ByteString] to utilize these new capabilities. One
problem here is the choice of the data type to be used for these
timestamps as the EpochTime type only allows granularity of one
second. One option might be POSIXTime from Data.Time.Clock.POSIX. I am
willing to provide patches.