Switch to C89 comments in prep for making the whole codebase C89 compatible.

This should be whitespace/comment only changes and should produce the same
object code.
Correct .gitignore to correctly account for build-aux.
Merge pull request #106

8ca6a9c Correct .gitignore to correctly account for build-aux. (Phillip Mienk)
Merge pull request #105

71712b2 Switch to C89 comments in prep for making the whole codebase C89 compatible. (Gregory Maxwell)