(Build-)depend on git >= 2.22 to avoid memory leaked git being bundled or used

Note from Joey:
  git-annex still supports git 2.1, but operates in a degraded fashion.
  It would be better for backports of the debian package to also
  backport a newer git. This dependency is mostly expressing that,
  also that any users who might upgrade git-annex should also upgrade
  git.

  Also worth noting that the i386ancient autobuilder has git 2.1 on it
  (best I have been able to manage there), but luckily the epoch is
  bumped to 2, so the dependencies will still be satisfied.

debian/patches/standalone-build

@@ -7,7 +7,7 @@ Last-Update: 2015-04-20
 --- a/debian/control
 +++ b/debian/control
 @@ -85,6 +85,7 @@ Build-Depends:
- 	git (>= 1:1.8.1),
+ 	git (>= 1:2.22),
  	rsync,
  	curl,
 +	locales,
@@ -23,7 +23,7 @@ Last-Update: 2015-04-20
  Architecture: any
  Section: utils
 -Depends: ${misc:Depends}, ${shlibs:Depends},
--	git (>= 1:1.8.1),
+-	git (>= 1:2.22),
 +Conflicts: git-annex
 +Provides: git-annex
 +Depends: ${misc:Depends},