procfs.c: Move find_signalled_thread and find_stop_signal.

procfs.c: Move find_signalled_thread and find_stop_signal.

These two functions are only used from procfs_make_note_section, which
itself is only defined if:

    #if defined (UNIXWARE) || defined (PIOCOPENLWP) || defined (PCAGENT)

So these two functions are unused on mips-irix, and they get flagged
by -Wunused-function. This patch simply moves these functions closer
to the function that uses them, which also has the effect of putting
them inside the same #if block as procfs_make_note_section.  Thus
they are defined only when used.

gdb/ChangeLog:

        * procfs.c (find_signalled_thread, find_stop_signal): Move
        these functions down to define them only when used.