Twice now I have had this problem while building native mysql bindings on my MacBook. I'm running OSX 10.4.8 and I can't remember which version of the xcode tools.
When you try and compile your bindings you will get an error message saying something like "ulong is undefined". The first time I got it was building the ruby mysql lib and I got it again this weekend building the perl dbi::mysql package.
The quickest workaround is to just do a quick search of the source file that threw the error - in the case with ruby it was mysql.c somewhere deep in my gems directory. Find the header file, mysql.h in this case, and insert the line
define ulong unsigned long
That did the trick in both cases. I'm glad I remembered it from the last time I saw it, I don't have the internet at home and had to get some Perl work done - CPAN is very very difficult to work with on just a few flying visits to cafes with wifi.