PID: minor macro updates.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2810 ba6dc0ae-232f-0410-883f-9ebac64fc565
fopen/fclose: Support GLIBC_2.1 version on i386.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2811 ba6dc0ae-232f-0410-883f-9ebac64fc565