run-tests: convert windows paths to unix

tests: make (glob) on windows accept \ instead of / Globbing is usually used for filenames, so on windows it is reasonable and very convenient that glob patterns accepts '\' or '/' when the pattern specifies '/'.

tests: use 'hghave serve' to guard tests that requires serve daemon management

tests: use 'hghave system-sh' to guard tests that requires sh in system()

tests: use 'hghave no-windows' to avoid testing reserved file names on windows

tests: use 'hghave unix-permissions' for tests that really use chmod chmod of helper scripts is not included. tests that exercise the x bit in the file system uses 'hghave execbit'.

tests: use 'hghave execbit' for tests that manipulate x bit in file system

tests: use 'hghave symlink' for tests using symlinks

windows: use umask 022 in debugstate output debugstate would always report files as mode 666 or 777 on Windows. umask is not used on Windows, but faking and using a defalt value of 022 matches what the test suite uses on Unix.

dispatch: exit with 8-bit exit code The exit code returned from a program to the shell is unsigned 8-bit, but Mercurial would sometimes try to exit with negative numbers or None. sys.exit on Unix will convert that to 8-bit exit codes, but on Windows negative values showed up as 0. The exit code is now explicitly converted to unsigned 8-bit.