Clean up .h declarations
- off64_t -> __off64_t
- threadinfo.h:  ADD: #include "syscallwrappers.h"  /* for _real_syscall */
- syscallwrappers.h:  Remove __GNU_SOURCE, and add POSIX-required declaration:
					 typedef void (*sighandler_t)(int);



git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2552 ba6dc0ae-232f-0410-883f-9ebac64fc565