libc/glibc: repair debugging with gdb (glibc 2.9)

Without this patch, crosstool-ng-built glibc-2.9 prevents
debugging any exeutable with gdb.
gdb says:
[Thread debugging using libthread_db enabled]
find_new_threads_callback: cannot get thread info: generic error
See also https://bugzilla.redhat.com/show_bug.cgi?id=487212
for a discussion of the bug and the solution.

 This is NOT the official version of dialog.  This version has been

 significantly modified from the original.  It is for use by the Linux

 kernel configuration script.  Please do not bother Savio Lam with 

 questions about this program.