Squashed 'm4/' content from commit 5d32f6c

git-subtree-dir: m4
git-subtree-split: 5d32f6cd68a1f31b01aedc417f627b454b089599
Merge commit '8189f07703d87a45aa4b6e047a1c935fec523995' as 'm4'
Put gphoto-m4 into m4/ subdir (not m4m)

With git, the subversion deficiency forcing us
to use m4m/ in the past has disappeared.
gitignore: Add .gitignore files