configure.ac: bump to version 1.7.92 for the RC1 release
configure.ac: bump to version 1.7.92 for the RC1 release

mchalupa/weston,sir-murray/weston,eyolfson/weston,mchalupa/weston,Tarnyko/weston-xdg_surface_present,Tarnyko/weston-xdg_surface_present,giucam/weston,Gnurou/weston,Fantu/compositor-spice,udoprog/weston,kwm81/weston,giucam/weston,krezovic/weston,jonnylamb/weston,krezovic/weston,jonnylamb/weston,Fantu/compositor-spice,eyolfson/weston,udoprog/weston,sir-murray/weston,Gnurou/weston,kwm81/weston,xorgy/weston,Fantu/compositor-spice,xorgy/weston