patch 8.1.1290: .hgignore and .gitignore are either distributed or in git

Problem:    .hgignore and .gitignore are either distributed or in git, not
            both.
Solution:   Add .gitignore to the distribution and .hgignore to git.  Update
            the entries. (Christian Brabandt, Ken Takata)
diff --git a/Filelist b/Filelist
index 7189278..23dfa3f 100644
--- a/Filelist
+++ b/Filelist
@@ -3,6 +3,7 @@
 
 # source files for all source archives
 SRC_ALL =	\
+		.gitignore \
 		.hgignore \
 		.lgtm.yml \
 		.travis.yml \