Consistently use equality for registration lookup.
#main object logics
src/Pure
src/FOL
src/HOL
src/ZF
src/CCL
src/CTT
src/Cube
src/FOLP
src/HOLCF
src/LCF
src/Sequents
#misc components
src/Tools/Code
src/Tools/WWW_Find
src/HOL/Tools/ATP_Manager
src/HOL/Mirabelle
src/HOL/Library/Sum_Of_Squares
src/HOL/Tools/SMT