Add .gitignore entry for a derived file created by "make distprep".

tglsfdc · tglsfdc · commit f6cddbd4d7c0 · 2019-01-10T14:20:28.000-05:00
I chanced to notice that "make distprep" leaves a state of the
tree that git complains about.  It's been like this for awhile,
but given the lack of complaints it probably doesn't need
back-patching.
diff --git a/src/interfaces/libpq/.gitignore b/src/interfaces/libpq/.gitignore
@@ -1,5 +1,6 @@
 /exports.list
 /libpq.rc
+/libpq-dist.rc
 # .c files that are symlinked in from elsewhere
 /encnames.c
 /wchar.c
