Fix BuildTestSuiteDetailedV09 on GHC <7.6
Describe concerns for PackageTests authors.
Trailing newline.
A fix for my previous fix for 'getSourceFiles'.

Apparently, lazy I/O was involved after all. 'openFile' instead of 'withFile'
was deliberate - see the use of 'unsafeInterleaveIO' in
'packageIndexFromCache'. Fixed by adding a strict version of 'getSourceFiles'.
Revert the timestamp checks back to (>=) from (>).
Work around the low clock resolution problem of 'getModificationTime'.

See http://hackage.haskell.org/trac/ghc/ticket/7473 .
Unbreak 'tryCanonicalizePath' on Windows.
Mark the '.cabal-sandbox' dir as hidden on Windows.
Merge pull request #1297 from ttuegel/test-inplace-lib

Fix BuildTestSuiteDetailedV09 on GHC <7.6
Merge pull request #1301 from 23Skidoo/getmodtime-and-other-fixes

Workaround for low clock resolution problem of `getModificationTime` + other fixes