Defines starting with `d' in bsd/nfs

• DIRHDSIZ bsd/nfs/nfs_vnops.c:369
• DO_BOOTP bsd/nfs/nfs_boot.c:272
• DRT_CACHEDROP bsd/nfs/nfsrtt.h:107
• DRT_CACHEREPLY bsd/nfs/nfsrtt.h:106
• DRT_NFSV3 bsd/nfs/nfsrtt.h:108
• DRT_NQNFS bsd/nfs/nfsrtt.h:104
• DRT_TCP bsd/nfs/nfsrtt.h:105