Added wrapper-locks arnd mkstemp(), etc.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2746 ba6dc0ae-232f-0410-883f-9ebac64fc565
Fix for file related wrappers to handle NULL path.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2747 ba6dc0ae-232f-0410-883f-9ebac64fc565
Added syscall-tester to test suite.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2748 ba6dc0ae-232f-0410-883f-9ebac64fc565