print reason for file handle creation failure

[pabs3]

In AsyncFileReader.h class AsyncFileIO function Initialize, it handles failure to open the file by printing an error saying that the file handle couldn't be created, but it doesn't print the reason for the error. This can be printed by printing the string returned by a strerror(errno) function call.

[pabs3]

This will be helpful to diagnose the SPTAG build failures in Debian.