fix a bunch of compiler warnings
remedy some code failures

(not sure about the effects)
fix playerState_t::misc field updates not getting through in all cases

who the fuck removed this change-check anyway?
fix the inconsistency between the enumarators and the strings of the means of death values

notably, this fixes crashes that occur when buildables self-destruct after losing creep
separate MISC_INFOHEAD into 2 fields, because a single 16-bit field is not enough to store 2 entity numbers (20 bits)
fix the crash that occurs, for example, when selecting a cuboid to build

this also possibly fixes "relaying cuboids"

also add proper declarations for related functions
fix a nonsensical condition
remove G_CheckCuboidConfig() until it is fixed