MFP4 (108673, 110519, 110874):

MFP4 (108673, 110519, 110874):
- Currently LINUX_MAX_COMM_LEN is smaller than MAXCOMLEN, but in case
  this will change we have a buffer overflow. Apply some defensive
  programming to DTRT when this should happen.
- Use copyinstr() instead of copyin where appropriate.
  * Fallback to copyin() in case of ENAMETOOLONG. [1]
  * Use the right source and destination (it was wrong before).
- Use strlcpy instead of strcpy.
- Properly lock the read case (PR_GET_NAME) like the write case.

Reviewed by:	rwatson (except [1])
Suggested by:	rwatson [1]