hppa NPTL switch - bump minimal libc6 requirements to "libc6 (>= 2.10)"

[Petr Salinger <Petr.Salinger@seznam.cz>]

Hi,

please do not forget to bump minimal libc6 requirements to
"libc6 (>= 2.10)" in libc6.symbols.hppa similarly as
in libc6.symbols.sparc.

The hppa NPTL switch is 100% *** backward *** compatible.
The pthread static initializers compiled against NPTL
will not work against linuxthreads (e)glibc.

Bump at least libpthread.so.0 and libthread_db.so.1
or be cautious and bump all libraries.

Petr