divide by zero while parsing kernel headers

hello!

I'm using makedepend to create a list of headers that need to be fed into exuberant-ctags in order to have sourcecode navigation within vim. it so happens I started to write kernel code, so while makedepending I reach a cornercase in which a pre-processor directive depends on the evaluation of MSEC_PER_SEC % HZ in which HZ is undefined in my case (see backtracebacktrace.txt #16).

this triggers a modulo 0 operation within ifparser.c:306 and crashes the makedepend process.

a fix is provided as a merge request !12 (merged)

thanks, peter