Avoid conflict with gnulib open/close macros.

Avoid conflict with gnulib open/close macros.

On some systems, the gnulib configuration will decide to define open
and/or close as macros to replace the POSIX C functions.  This
interferes with using those names in C++ class or namespace scopes.

gdbsupport/
	* event-pipe.cc (event_pipe::open): Renamed to ...
	(event_pipe::open_pipe): ... this.
	(event_pipe::close): Renamed to ...
	(event_pipe::close_pipe): ... this.
	* event-pipe.h (class event_pipe): Updated.
gdb/
	* inf-ptrace.h (async_file_open, async_file_close): Updated.
gdbserver/
	* gdbserver/linux-low.cc (linux_process_target::async): Likewise.