LU-2675 lnet: add lnet/nidstr.h

LU-2675 lnet: add lnet/nidstr.h

Add lnet/include/lnet/nidstr.h to break the include loop between
libcfs/libcfs.h and lnet/types.h. Where possible include lnet/types.h
or lnet/nidstr.h rather than lnet/lnet.h. Remove the unneccessary
headers lnet/{,darwin/,linux/}api-support.h.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Ide4cd79295eba8705c0d413449cbb812343cbec9
Reviewed-on: http://review.whamcloud.com/11506
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-by: Amir Shehata <amir.shehata@intel.com>
Reviewed-by: Isaac Huang <he.huang@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>