makedef: Port to Bourne Shell

Perl is an unnecessary dependency. This is the first step towards inclusion in the Libav source tree. It may be a bit hard to review it as a "patch" like this — you can view the file as-is at:

https://github.com/dwbuiten/c99-to-c89/blob/makedef-rewrite/makedef

@mstorsjo & @rbultje Please review.

I will push it when both of you are satisfied with it.

\- Derek