libbe(3)/bectl(8): More SYSROOT/GCC build fixes

- Missing include path
- Fully specify libzfs's dependencies (except for deps pulled in by other
  deps) in Makefile.inc1
- Drop WARNS back down to 2 for libbe(3). I do this with much hesitation,
  but the libzfs headers are apparently a hot warning-filled mess as far as
  GCC 4.2 is concerned.

Makefile.inc1

@@ -2598,7 +2598,13 @@ _cddl_lib_libuutil= cddl/lib/libuutil
 .if ${MK_ZFS} != "no"
 _cddl_lib_libzfs_core= cddl/lib/libzfs_core
 _cddl_lib_libzfs= cddl/lib/libzfs
+
 cddl/lib/libzfs_core__L: cddl/lib/libnvpair__L
+
+cddl/lib/libzfs__L: cddl/lib/libzfs_core__L lib/msun__L lib/libutil__L
+cddl/lib/libzfs__L: lib/libthr__L lib/libmd__L lib/libz__L cddl/lib/libumem__L
+cddl/lib/libzfs__L: cddl/lib/libuutil__L cddl/lib/libavl__L lib/libgeom__L
+
 cddl/lib/libbe__L: cddl/lib/libzfs__L
 .endif
 _cddl_lib_libctf= cddl/lib/libctf

cddl/lib/libbe/Makefile

@@ -11,6 +11,8 @@ SRCS=		be.c be_access.c be_error.c be_info.c
 INCS=		be.h
 MAN=		libbe.3
 
+WARNS?=	2
+
 LIBADD+= zfs
 LIBADD+= nvpair
 

sbin/bectl/Makefile

@@ -13,6 +13,7 @@ LIBADD+= util
 CFLAGS+= -I${SRCTOP}/cddl/contrib/opensolaris/lib/libzfs/common
 CFLAGS+= -I${SRCTOP}/sys/cddl/compat/opensolaris
 CFLAGS+= -I${SRCTOP}/sys/cddl/contrib/opensolaris/uts/common
+CFLAGS+= -I${SRCTOP}/cddl/contrib/opensolaris/lib/libnvpair
 
 CFLAGS+= -DNEED_SOLARIS_BOOLEAN