Miscellaneous minor fixes/improvements.

Most notable is that the rundiff trace-output lossage is fixed!

base/pollevent.cc:
    Use SA_RESTART to keep blocked write() calls from failing
    with EINTR when signals happen.
base/trace.hh:
    Make TRACING_ON depend on NDEBUG not being set (instead of
    DEBUG being set) so m5.opt/m5.fast do what we want.
util/rundiff:
    Print header lines showing file/cmd names.

--HG--
extra : convert_revision : 4966814ad65aedb6d62a5a62a6ad3e3f326d61b8

util/rundiff

@@ -87,6 +87,10 @@ my ($fh1, $fh2);
 open($fh1, $file1) or die "Can't open $file1";
 open($fh2, $file2) or die "Can't open $file2";
 
+# print files to output so we know which is which
+print "-$file1\n";
+print "+$file2\n";
+
 # buffer of matching lines for pre-diff context
 my @precontext = ();
 # number of post-diff matching lines remaining to print