Fix build issues on NetBSD where the reg symbol exists in public headers. regformats/regdef.h:22:8: error: redefinition struct struct reg ^~~ /usr/include/amd64/reg.h:51:8: note: previous definition struct struct reg { ^~~ gdb/ChangeLog: * regformats/regdef.h: Put reg in gdb namespace. gdbserver/ChangeLog: * regcache.cc (find_register_by_number): Update. * tdesc.cc (init_target_desc): Likewise. * tdesc.h (target_desc::reg_defs): Likewise.