* cygheap_malloc.h: New file.

* cygheap_malloc.h: New file.
* cygheap.h: Remove stuff now included in cygheap_malloc.h and include that
file.  Make cygheap_init a standard c++ function.  Remove unneeded child_info
declaration.
* path.h: Include cygheap_malloc.h.  Remove extra cstrdup declaration.
(path_conv): Reorganize to group variables together.
(path_conv::path): Make const char *.
(path_conv::known_suffix): Ditto.
(path_conv::normalized_path): Ditto.
(path_conv::path_conv): Reorganize initializers to reflect new element
ordering.
(path_conv::get_win32): Change return value to const char *.
(path_conv::set_path): Move back here from spawn.cc.
(parh_conv::modifiable_path): New function.
* path.cc (path_conv::add_ext_from_sym): Accommodate const'ness of
known_suffixes.
(path_conv::set_normalized_path): Ditto for normalized_path.
(path_conv::check): Use modifiable_path whereever we need to modify the path
element.  Use set_path to set the path.
(path_conv::~path_conv): Accommodate new const'ness.
* spawn.cc (perhaps_suffix): Declare ext as const since that's what is being
returned.
(path_conv::set_path): Move back to path.h.
* winf.f (linebuf): Perform minor cleanup.
(linebuf::fromargv): Change second parameter to const.
* winf.cc (linebuf::fromargv): Ditto.