base.bbclass: Add buildcfg multilib values

base.bbclass: Add buildcfg multilib values

When displaying the buildcfg for the end user, add in processing
of the multilib variants.  Only the items that are not the same as
the DEFAULTTUNE are displayed.

I.e.:
Build Configuration:
BB_VERSION        = "1.19.0"
BUILD_SYS         = "x86_64-linux"
NATIVELSBSTRING   = "CentOS-6.4"
DISTRO_VERSION    = "oe-core.0"
MACHINE           = "qemux86-64"
DEFAULTTUNE       = "x86-64"
TARGET_SYS        = "x86_64-oe-linux"
TUNE_FEATURES     = "m64"
TARGET_FPU        = ""
lib32:  DEFAULTTUNE       = "x86"
lib32:  TARGET_SYS        = "i586-oe-linux"
lib32:  TUNE_FEATURES     = "m32"
meta              = "master:1975f3d7bbeb184489a5d0a2e0de231f317d3e1b"

The order of the displayed elements was changed slightly to group the
host information together, as well as group the target information
together.

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Robert Yang <liezhi.yang@windriver.com>