Enable building on OSX.
System-dependant path name separators are now used in
FileWrapperImplTest instead of a hardcoded backslash.
Two tests with very system-dependant behavior were removed from FileTest.
One, a test for equeals, fails on OSX installs which have
The other test - an attempt to create an "invalid" filename, simply fails on OSX
by allowing an example of a purportedly invalid filename, "/..", to be created
without throwing an exception.