cygwin: Fix crashes under AllocationPreference=0x100000 condition

* cygtls.h: Include cygtls_padsize.h and define CYGTLS_PADSIZE there.
        * cygtls_padsize.h: New file.  Define CYGTLS_PADSIZE.
        * environ.cc (parse_options): Fix NULL pointer access.
        * init.cc (threadfunc_fe): Do not force stack align on x86_64.

        * strace.cc (main2): Rename from main.
        (main): Make room for _cygtls area on stack and just call main2.  Add
        comment to explain why.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/init.cc

@@ -25,8 +25,10 @@ static bool dll_finished_loading;
 static void WINAPI
 threadfunc_fe (VOID *arg)
 {
+#ifndef __x86_64__
   (void)__builtin_return_address(1);
   asm volatile ("andl $-16,%%esp" ::: "%esp");
+#endif
   _cygtls::call ((DWORD (*)  (void *, void *)) TlsGetValue (_my_oldfunc), arg);
 }