Fix some missing .gitignore and "make clean" items in ecpg.

Tom Lane <tgl@sss.pgh.pa.us>

Commit: 52acfd27f11ca586f90c2c1255ca9a4a66766b57
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2014-02-19T23:50:48Z
Releases: 9.4.0
Fix some missing .gitignore and "make clean" items in ecpg.

Some of the files we optionally link in from elsewhere weren't ignored
and/or weren't cleaned up at "make clean".  Noted while testing on a
machine that needs our version of snprintf.c.

Files