Attribute parse

Hi @jjallaire, actually I have a patched version in my computer for a while. Hope I didn't waste your time to investigate the issue. Please feel free to modify as needed.

Resolve #192 
Do you mean an union of c* and h*?

With scanHeaderFiles = TRUE, we get an union of c* and h*; with default scanHeaderFiles = FALSE, we only scan c*.

Should we just change the default behavior, rather than add an argument to control the behavior?