32-bit Windows (issues 256 through 263)

256: Merge Windows version into single codebase
257: Set Environment Variable (_setenv) fails in Windows
258: String Match (_sm) fails in Windows
259: Gaps in MINGW32_NT-6.x
260: K banner for Windows binaries
261: String Match (_sm) case
262: Command version of dyadic 4: fails in Windows
263: _sm has a memory leak