arch: add provides=('powerline') to PKGBUILDs.

packages/archlinux/python-powerline-git/PKGBUILD

@@ -15,6 +15,7 @@ optdepends=('python-psutil: improved system information'
 	'python-pygit2: improved git support'
 	'zsh: better shell prompt'
 	'gvim: vim compiled with Python support')
+provides=('powerline')
 conflicts=('python2-powerline-git'
 	'powerline-git')
 install="${_gitname}.install"

packages/archlinux/python2-powerline-git/PKGBUILD

@@ -16,6 +16,7 @@ optdepends=('python2-psutil: improved system information'
 	'mercurial: improved mercurial support'
 	'zsh: better shell prompt'
 	'gvim: vim compiled with Python support')
+provides=('powerline')
 conflicts=('python-powerline-git')
 replaces=('powerline-git')
 install="${_gitname}.install"