test_fsync made modular

I have modified test_fsync to use modular C so there is less duplicate
code and it can be enhanced easier. Applied patch attached, though the
diff is larger than the C file so you might want to just look at the C
file in git.

--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +