core.sys.windows.windows: Add file locking APIs
core.stdc.stdio: Add MSVCRT functions to convert between fds and HANDLEs
Merge pull request #700 from CyberShadow/windows-locks

core.sys.windows.windows: Add file locking APIs
Merge pull request #701 from CyberShadow/osfhandle

core.stdc.stdio: Add MSVCRT functions to convert between fds and HANDLEs
core.sys.windows.windows: Add ERROR_ALREADY_EXISTS
Merge pull request #702 from CyberShadow/error_already_exists

core.sys.windows.windows: Add ERROR_ALREADY_EXISTS