Add refs to Chocolatey for dependency installation

This patch modifies the windows installation instructions to include
references to [Chocolatey](https://chocolatey.org) as a simple way to
install many of the pre-requisites required by this toolset. It is
quickly becoming my favorite method for managing open source packages on
windows.
Fix complaint when editing multiple C files

`after/ftplugin/c.vim` now forces the redefinition of `:Cscope` every
time a new .c or .cpp file is opened. This prevents weird errors when
opening new .c or .cpp files.