procfs.c: Remove unused functions and make many functions static

procfs.c: Remove unused functions and make many functions static

gdb/ChangeLog:

        * procfs.c (procfs_find_new_threads, procfs_pid_to_str,
        proc_warn, proc_error, proc_get_status, proc_flags,
        proc_why, proc_what, proc_nsysarg, proc_sysargs,
        proc_set_run_on_last_close, proc_unset_run_on_last_close,
        proc_unset_inherit_on_fork, proc_set_async, proc_unset_async,
        proc_stop_process, proc_wait_for_stop, proc_run_process,
        proc_set_traced_signals, proc_set_traced_faults,
        proc_set_traced_sysentry, proc_set_traced_sysexit,
        proc_set_held_signals, proc_get_held_signals,
        proc_get_traced_signals, proc_get_traced_faults,
        proc_get_traced_sysentry, proc_get_traced_sysexit,
        proc_clear_current_fault, proc_set_current_signal,
        proc_clear_current_signal, proc_get_gregs, proc_get_fpregs,
        proc_set_gregs, proc_set_fpregs, proc_kill, proc_parent_pid,
        proc_get_nthreads, proc_get_nthreads, proc_get_nthreads,
        proc_get_current_thread, proc_get_current_thread,
        proc_get_current_thread, proc_update_threads,
        proc_update_threads, proc_update_threads, proc_update_threads,
        proc_iterate_over_threads, procfs_find_new_threads,
        procfs_pid_to_str): Make static.  Remove advance declaration.
        (proc_cursig): Make static.  Conditionalized defintion on
        PROCFS_DONT_PIOCSSIG_CURSIG being defined.
        (proc_syscall, proc_set_kill_on_last_close,
        proc_unset_kill_on_last_close, proc_set_inherit_on_fork,
        proc_get_pending_signals, proc_get_signal_actions,
        proc_trace_signal, proc_ignore_signal): Delete.