* path.cc (cwd_win32): Eliminate.

* path.cc (cwd_win32): Eliminate.
(cwd_posix): Eliminate.
(cwd_hash): Eliminate.
(cwdstuff::init): Rename from cwd_init.
(cwdstuff::fixup_after_exec): Rename from cwd_fixup_after_exec.
(cwdstuff::get): Rename from get_cwd_inner.
(normalize_posix_path): Eliminate cwd argument.  Just calculate when necessary.
(normalize_win32_path): Ditto.
(mount_info::conv_to_win32_path): Eliminate cwd retrieval here.
(mount_info::conv_to_posix_path): Ditto.
(hash_path_name): Accomodate additional methods in cwdstuff.
(get_cwd_win32): Eliminate.
(getcwd): Use cwdstuff methods.  Properly handle case where buf == NULL and len
< 0.
(cwdstuff::get_hash): New method.
(cwdstuff::get_initial): New method.
(cwdstuff::set): New method.
(cwdstuff::get): New method.
(cwdstuff::copy): New method.
* path.h: Move cwdstuff struct here.  Add a bunch of stuff to cwdstuff.  Make
cygcwd an extern.
* spawn.cc (spawn_guts): Use copy method to get copies of cwd info to pass to
execed process.
* dcrt0.cc (dll_crt0_1): Use cygcwd methods for cwd initialization.