Handle MAKEENTRY cnp flag in the VOP_CREATE().  Curiously, some
fs, e.g. smbfs, already did it.

Tested by:	pho (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Add VN_OPEN_NAMECACHE flag for vn_open_cred(9), which requests that
the created file name was cached.  Use the flag for core dumps.

Requested by:	rpaulo
Tested by:	pho (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks