introduce parallel mode

introduce parallel mode

This introduces parallel mode for the test suite.

It doesn't fully work yet in the sense that if you do a fully parallel
run, you will encounter some file-name clashes, but this has to start
somewhere, and it seemed best to add some infrastructure now, so that
you can follow along and test subsequent patches if you care to.

This patch has two parts.

First, it checks for the GDB_PARALLEL variable.  If this is set (say,
on the runtest command line), then the test suite assumes "parallel
mode".  In this mode, files are put into a subdirectory named after
the test.  That is, for DIR/TEST.exp, the outputs are put into
./outputs/DIR/TEST/.

This first part has various follow-on changes coming in subsequent
patches.  This is why the code in this patch also makes "temp" and
"cache" directories.

Second, this adds an "inotify" mode.  If you have the inotifywait
command (part of inotify-tools), you can set the GDB_INOTIFY variable.
This will tell the test suite to watch for changes outside of the
allowed output directories.

This mode is useful for debugging the test suite, as it issues a
report whenever a possibly parallel-unsafe file open is done.

2013-08-13  Tom Tromey  <tromey@redhat.com>
	    Yao Qi  <yao@codesourcery.com>

	* lib/cache.exp (gdb_do_cache): Handle GDB_PARALLEL.
	* lib/gdb.exp: Handle GDB_PARALLEL.
	(default_gdb_version): Kill inotify_pid if it exists.
	(default_gdb_exit): Emit warning if the inotify log is not
	empty.
	(standard_output_file): Respect GDB_PARALLEL.
	(standard_temp_file): Likewise.
	(gdb_init): Start inotifywait if requested.

	* gdbint.texinfo (Testsuite): Use @table, not @itemize.
	Document GDB_PARALLEL and GDB_INOTIFY.