msvc: Add configurations with /MT compilation flag

Allows statically linking vc++ runtime dependencies inside libusb-1.0
Windows libraries.

'Release' and 'Debug' configurations produce /MD compiled binaries while
the new 'Release-MT' and 'Debug-MT" configurations produce /MT compiled
binaries.

The /MT flag causes the application to include the multithread, static
version of the vc++ run-time library, whereas the default flag /MD will
cause the vc++ run-time library to be dynamically linked run-time. Using
/MT thus builds a standalone libusb DLL that doesn't require a vc++
runtime DLL to be shipped along with it.

For the official description of /MT see:
https://docs.microsoft.com/en-us/cpp/build/reference/md-mt-ld-use-run-time-library

Closes #1188