* cygheap.h (cygheap_fdmanip::cygheap_fdmanip): Clear fh.

(cygheap_fdmanip::isopen): New method.
* syscalls.cc (_read): Avoid accessing closed fd.
* path.h (fe_types): New enum.
(path_conv::set_path): New method.
(find_exec): Change null_if_not_found argument to something more generic.
* spawn.cc (find_exec): Default to returning the POSIX path rather than the
windows path, unless instructed otherwise.
(spawn_guts): Force call to find_exec to use native paths.
* dlfcn.cc (check_path_access): Accommodate new find_exec arguments.
* environ.h (win_env::get_posix): New method.

winsup/cygwin/dlfcn.cc

@@ -38,7 +38,7 @@ set_dl_error (const char *str)
 inline const char * __stdcall
 check_path_access (const char *mywinenv, const char *name, path_conv& buf)
 {
-  return find_exec (name, buf, mywinenv, TRUE);
+  return find_exec (name, buf, mywinenv, FE_NNF | FE_NATIVE | FE_CWD);
 }
 
 /* Search LD_LIBRARY_PATH for dll, if it exists.