use shears to clean up v1.9.2.msysgit

Hello,
I ran `/share/msysGit/merging-rebase.sh --force v1.9.2` and edited the rebase script to fit my previously submitted changes in the `win-tests-fixes` branch.
The rebase script is [available here](http://www.ucw.cz/~kasal/msysgit/shears-script5)

The result is this `kasal/git/master`.
I have verified that the source tree is as intended (diff against my previous patched master).
I have also verified that testsuite passes (skipping t5000, t5003, t9300, t91*, because these caused problems previously).

This branch is intended as a fast-forward for msysgit/git/master, so that it represents a new rebase on v1.9.2.

Update: shears-script5 changes only one detail: the final commit "Avoid bash-ism" is attached as a fixup to the commit that introduced the issue ("Win32: support long paths").

(Working with shears.sh was really fun, I'm willing to redo this if you find a mistake in this version; I'll be back online on Tuesday.)

(The previous versions of my `shears-script` are all available [in this dir](http://www.ucw.cz/~kasal/msysgit/), and the corresponding results are in repo `kasal/git` as `master-4th`, `master-3rd`, etc.
So if you are not happy with my latest version, a previous one might be ok.)