* path.cc (mount_info::conv_to_posix_path): Avoid putting a trailing slash on a

* path.cc (mount_info::conv_to_posix_path): Avoid putting a trailing slash on a
directory name when the ms-dos path spec is a root directory of a device.
* registry.cc (reg_key::build_reg): Set 'key_is_invalid' flag rather than using
an INVALID_HANDLE_KEY.
(reg_key::get_int): Test for key validity before performing registry
operations.
(reg_key::set_int): Ditto.
(reg_key::get_string): Ditto.
(reg_key::set_string): Ditto.
(reg_key::kill): Ditto.
(reg_key::~reg_key): Ditto.