Ferite profiling

RUn configure with --enable-profile, then

    $ ferite --fe-profile=out.json <file.fe>

Feed out.json to fprof[1] to produce the html reports.

Profile metrics are saved into the given file at atexit(3)

[1] https://github.com/cention-nazri/fprof
Add line field in FeriteFunction

native_information->line holds the same information, there were no
equivalent information for non-native functions.

Eventually these two locations should be consolidated as one - the next
commit after this one will do it.
Consolidate line field information for native and non-native functions
Expand "%i" in profile filename pattern to process id
Avoid possible segfault when saving profiling data

Saving profiling data atexit(3) may cause a segfault due to
ferite_deinit() being called before ferite_profile_save() - the memory
allocated for the profiling metrics may have been freed by the garbage
collector.

Provide an api for saving the profiling data at exit for use by clients
such as mod_ferite.