Move dmtcp_<plugin>_enabled() to util.h.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2759 ba6dc0ae-232f-0410-883f-9ebac64fc565
dmtcpalloc.h: include sstream for stringstream.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2760 ba6dc0ae-232f-0410-883f-9ebac64fc565
Coord: Send compId with SUSPEND msg.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2761 ba6dc0ae-232f-0410-883f-9ebac64fc565
Simplify ckpt{dir,file} related code.

- Moved to processinfo.cpp.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2762 ba6dc0ae-232f-0410-883f-9ebac64fc565
Created unique-ckpt plugin.

- disabled by default.
- --enable-unique-ckpt-filenames automatically enables this plugin.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2763 ba6dc0ae-232f-0410-883f-9ebac64fc565