rename stringpatch to stringreplace

to avoid requiring admin rights in win32, see
https://cygwin.com/ml/cygwin/2014-03/msg00191.html and https://github.com/JuliaLang/julia/pull/7736#commitcomment-7164355 for background

The fact that this has never been reported (permissions denied running stringpatch) indicates no one has tried running `make install` in a from-source 32 bit MSYS build on Windows...

We could add a manifest file instead to prevent this, but we'd need to worry about installing it to `$(build_bindir)`. This is easier, but entirely deserving of commentary on how strange Windows is.

Cygwin fixed this problem in March (their binutils does the manifest automatically now) so I forgot about it, but it's still an issue in MSYS2. cc @staticfloat