Add macros to check if a filename is a WAL segment or other such file.

Heikki Linnakangas <heikki.linnakangas@iki.fi>

Commit: 179cdd098196338880bdbb39c39a788abdad4dd8
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: 2015-05-08T18:58:57Z
Releases: 9.5.0
Add macros to check if a filename is a WAL segment or other such file.

We had many instances of the strlen + strspn combination to check for that.
This makes the code a bit easier to read.

Files