v0.8.8

1. Upgrade mintty to 2.8.4 (2.8.2, 2.8.3).
2. Fix cmdtool wstartex path issues (detail).
3. Use mintty_options in run-wsl-file.exe and vim.exe.
4. Remove wpath and install cbwin subcommands of cmdtool.

If your wsl-terminal version number is higher than 0.8.0, can upgrade it with ./cmdtool update (usage).

sha256sum	filename
bb528b76970dd4c57729eff93ff223240db45b9f67b70f8394132d9061f92048	wsl-terminal-0.8.8.7z
42f0a48d0b1a645985b2a569ca44e534f9aa685baeab6d6fd8b79c3ad7e6fc77	wsl-terminal-0.8.8.zip