* path.h (cwdstuff): Move class.

* path.h (cwdstuff): Move class.
* cygheap.h (cwdstuff): To here.
(init_cygheap): Add cwd field.
* child_info.h (cygheap_exec_info): Eliminate cwd stuff.
(child_info_spawn): Ditto.
* dcrt0.cc (dll_crt0_1): Remove cygcwd.fixup_after_exec call.  Convert cygcwd
reference to cygheap->cwd.
* path.cc: Ditto, throughout.
(cwdstuff::copy): Eliminate.
(cwdstuff::fixup_after_exec): Ditto.
* spawn.cc (spawn_guts): Eliminate call to cygcwd.copy.
* fhandler.h (FH_OSS_DSP): Move into "fast" device category.