Sharpend the DMTCP/MTCP divide

- All of the code required to generate mtcp_restart is now in src/mtcp/
- All code in src/ is _only_ for libdmtcp.so and friends.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2677 ba6dc0ae-232f-0410-883f-9ebac64fc565