Change both sites, not one

This caused "zero length packet" in client.
Begin to trim skills.
Remove all non-NPC skills
Remove PC/mob disguises and hard-coded classes
Clean up some things after declassization
Purge some more stuff that can't happen
Remove hard-coded mob stuff, make mode enum
Fix build with clang against libstdc++ 4.6
Remove unnecessary includes, speeding up recompilation
Remove most other unused mob skills.
Remove most of the unused StatusChange values
Remove some more Skill-related stuff
Remove some macros
Strictify timers
Replace mt_rand with <random>

Also add some utility methods and classes.
Rotate logs in background

Also reenable the critical bonus effect.
Strictify map cells

Also fix a small but major bug in map_randfreecell.
Replace struct dbt with typesafe std::map wrappers

Also fix broken save/accreg.txt reading.
Fix buffer overflow due to off-by-one error
Fix walk bug exposed by assertion