Use hMainProc where appropriate, throughout.

* environ.cc (spenv::retrieve): Add debugging statements.
* pinfo.cc (set_myself): Don't call strace.hello if already stracing.
* strace.cc (strace): Move NO_COPY keyword so that it will actually take
effect.

winsup/cygwin/uinfo.cc

@@ -43,8 +43,7 @@ internal_getlogin (cygheap_user &user)
 
       /* Try to get the SID either from current process and
 	 store it in user.psid */
-      if (!OpenProcessToken (GetCurrentProcess (),
-			     TOKEN_ADJUST_DEFAULT | TOKEN_QUERY,
+      if (!OpenProcessToken (hMainProc, TOKEN_ADJUST_DEFAULT | TOKEN_QUERY,
 			     &ptok))
 	system_printf ("OpenProcessToken(): %E\n");
       else if (!GetTokenInformation (ptok, TokenUser, &tu, sizeof tu, &siz))