Squashed 'bundle/bufstop-search/' changes from a0c8eef..3a61cbb

3a61cbb using vim-shell when available

git-subtree-dir: bundle/bufstop-search
git-subtree-split: 3a61cbb5359d445f931c5df8c5730e5945d4ac62
Merge commit 'fa0a597bcb999cf7e3b57671102f396e0174e0e3'
updates