RELENG_6 compilation issues

[Vlad GALU]

  Seems that rev. 1.114.2.4 of devfs_vnops.c broke the kernel build,
due to a few structures' forward declarations (devfs_ops_f,
devfs_vnodeops, devfs_specops). An excerpt from /etc/make.conf:

-- cut here --
CPUTYPE?=p4
CFLAGS= -O2 -pipe
CXXFLAGS+= -O2 -pipe -ffast-math
BDECFLAGS=      -W -Wall -ansi -pedantic -Wbad-function-cast -Wcast-align \
                -Wcast-qual -Wchar-subscripts -Winline \
                -Wmissing-prototypes -Wnested-externs -Wpointer-arith \
                -Wredundant-decls -Wshadow -Wstrict-prototypes -Wwrite-strings
COPTFLAGS= -O2 -pipe -ffast-math
-- and here --

-- 
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If it's not there, and you can see it, it's virtual.
If it's there, and you can't see it, it's transparent.
If it's not there, and you can't see it, you erased it.