update files to fparser 4.5.1
add threadsafe eval patch by Roy H. Stogner
Fix for fparser optimization with NaN

This probably isn't the only place where the optimizer is implicitly
assuming that values aren't NaN, but it's the only one I could find
and it's sufficient to fix my test case.
Define NaN for fparser
update generated files
Do not disable fparser optimizer on OSX
rerunning bootstrap
Merge pull request #239 from dschwen/fparser_4.5.1

Update to FParser 4.5.1