(2.9.8) Segfault during global constructor for std_istream at program start.

[Benjamin Kosnik]

This patch in, with changes.

Thanks scott.

2000-03-16  Benjamin Kosnik  <bkoz@cygnus.com>
            scott snyder  <sss@karma.fnal.gov>
	
	* config/c_io_libio.h: Add __c_lock.
	* config/threads-no.h: Same here.
	* config/threads-posix.h: Add __mutext_type typedef.
        * config/c_io_libio.cc: basic_file ctor takes lock arg. 
        * bits/basic_file.h: Ctor takes lock arg. 
        * bits/std_fstream.h: Add _M_lock.
        * bits/fstream.tcc: Supply it to basic_file ctor.