Help needed: fix build issue with xdxf_makedict in older platforms

[Leonardo Brondani Schenkel]

Hello all,

I recently introduced a new port, xdxf_makedict, which built 
successfully on my box (macOS 10.13) on first try. However, after it got 
merged I started getting notifications from the buildbots about build 
failures on 10.12 and older.

The first problem, which I now have solved, was that the code was using 
the EXIT_SUCCESS/EXIT_FAILURE macros in some files without including 
<cstdlib> first.

However, now I started getting other, different failures:
- 10.8: 
https://build.macports.org/builders/ports-10.8_x86_64_legacy-builder/builds/42330/steps/install-port/logs/stdio
- 10.7: same problem as 10.8
- 10.6: 
https://build.macports.org/builders/ports-10.6_x86_64_legacy-builder/builds/46675/steps/install-port/logs/stdio

The problem is that I cannot replicate any of this, and I don't have any 
older environment to test. So far I have been fixing the issues "blind" 
but I have committed two fixes already and I don't want to be committing 
fixes on top of fixes that might or might not solve the issue, polluting 
the history in the process.  Could somebody help?

This is kind of a fringe program, I have decided to add the port since I 
could build it on first try and thought it might be useful to others. 
But now I'm kinda disappointed with the state of the codebase and I'm 
starting to wonder if adding this was the right call...

// Leonardo.