(struct cursor): Replace rbs_top and top_rnat_loc with rbs_wridx, rbs_curr, 	rbs_nvalid, and rbs_area.  Add new member sigcontext_off.
(struct cursor): Replace rbs_top and top_rnat_loc with rbs_wridx, rbs_curr,
	rbs_nvalid, and rbs_area.  Add new member sigcontext_off.

(Logical change 1.40)

adsharma/libunwind,frida/libunwind,Keno/libunwind,fdoray/libunwind,pathscale/libunwind,wdv4758h/libunwind,unkadoug/libunwind,lat/libunwind,android-ia/platform_external_libunwind,ehsan/libunwind,djwatson/libunwind,Keno/libunwind,igprof/libunwind,CyanogenMod/android_external_libunwind,zliu2014/libunwind-tilegx,cms-externals/libunwind,mpercy/libunwind,mpercy/libunwind,rogwfu/libunwind,dreal-deps/libunwind,androidarmv6/android_external_libunwind,igprof/libunwind,fillexen/libunwind,rogwfu/libunwind,project-zerus/libunwind,wdv4758h/libunwind,atanasyan/libunwind,DroidSim/platform_external_libunwind,dagar/libunwind,zliu2014/libunwind-tilegx,atanasyan/libunwind-android,martyone/libunwind,project-zerus/libunwind,djwatson/libunwind,fdoray/libunwind,dagar/libunwind,bo-on-software/libunwind,evaautomation/libunwind,wdv4758h/libunwind,tronical/libunwind,tony/libunwind,jrmuizel/libunwind,martyone/libunwind,android-ia/platform_external_libunwind,Chilledheart/libunwind,cms-externals/libunwind,lat/libunwind,SyndicateRogue/libunwind,atanasyan/libunwind,krytarowski/libunwind,tronical/libunwind,joyent/libunwind,yuyichao/libunwind,pathscale/libunwind,djwatson/libunwind,cms-externals/libunwind,geekboxzone/mmallow_external_libunwind,frida/libunwind,atanasyan/libunwind-android,0xlab/0xdroid-external_libunwind,vegard/libunwind,geekboxzone/lollipop_external_libunwind,dropbox/libunwind,cloudius-systems/libunwind,martyone/libunwind,geekboxzone/lollipop_external_libunwind,adsharma/libunwind,SyndicateRogue/libunwind,rntz/libunwind,dreal-deps/libunwind,pathscale/libunwind,zeldin/platform_external_libunwind,libunwind/libunwind,maltek/platform_external_libunwind,zeldin/platform_external_libunwind,tronical/libunwind,unkadoug/libunwind,bo-on-software/libunwind,krytarowski/libunwind,rantala/libunwind,zliu2014/libunwind-tilegx,Chilledheart/libunwind,vegard/libunwind,adsharma/libunwind,bo-on-software/libunwind,Keno/libunwind,tony/libunwind,vtjnash/libunwind,dropbox/libunwind,olibc/libunwind,jrmuizel/libunwind,atanasyan/libunwind-android,cloudius-systems/libunwind,vtjnash/libunwind,CyanogenMod/android_external_libunwind,olibc/libunwind,lat/libunwind,geekboxzone/lollipop_external_libunwind,jrmuizel/libunwind,libunwind/libunwind,evaautomation/libunwind,tkelman/libunwind,ehsan/libunwind,rogwfu/libunwind,geekboxzone/mmallow_external_libunwind,rantala/libunwind,rantala/libunwind,CyanogenMod/android_external_libunwind,krytarowski/libunwind,igprof/libunwind,vtjnash/libunwind,dropbox/libunwind,project-zerus/libunwind,olibc/libunwind,0xlab/0xdroid-external_libunwind,cloudius-systems/libunwind,unkadoug/libunwind,maltek/platform_external_libunwind,DroidSim/platform_external_libunwind,androidarmv6/android_external_libunwind,DroidSim/platform_external_libunwind,android-ia/platform_external_libunwind,rntz/libunwind,fillexen/libunwind,fdoray/libunwind,yuyichao/libunwind,tony/libunwind,vegard/libunwind,joyent/libunwind,mpercy/libunwind,SyndicateRogue/libunwind,tkelman/libunwind,Chilledheart/libunwind,libunwind/libunwind,tkelman/libunwind,fillexen/libunwind,zeldin/platform_external_libunwind,dreal-deps/libunwind,frida/libunwind,maltek/platform_external_libunwind,ehsan/libunwind,geekboxzone/mmallow_external_libunwind,atanasyan/libunwind,androidarmv6/android_external_libunwind,yuyichao/libunwind,evaautomation/libunwind,dagar/libunwind,joyent/libunwind,0xlab/0xdroid-external_libunwind,rntz/libunwind