#67 c-fill-paragraph stopped working for // comments

[Andre Colomb]

In version 1.4.0, comments starting with // (or even /// like I use for doxygen) were correctly filled when pressing M-q (c-fill-paragraph).
This is no longer the case with 1.5.0. The broken lines are not prefixed as comments but instead end up as literal code.

Sample:
// this is a very long comment this is a very long comment this is a very long comment

is filled to:

// this is a very long comment this is a very long comment this is a
very long comment

Besides that, 1.5.0 is great, thanks!