New pln_att(), pln_def(), pln_acc(), pln_range_max(), pln_load()
replace the struct plnstr members with the same names.
Make plane selectors att and def virtual.
The macros defining unit stat development in tech are somewhat
inconvenient to use. Define more convenient functions, and hide away
the macros near the function definitions.
other. Ensure headers in include/ can be included in any order
(except for econfig-spec.h, which is special). New header types.h to
help avoid inclusion cycles. Sort include directives. Remove some
superflous includes.
files ship.config, plane.config, land.config, nuke.config.
(empfile): Declare the new config files.
(install, installdirs): Install them.
(builtins): New make variable.
Useless, remove. Users changed to check plchr's sentinel, because
that's clearer than comparing the index to N_MAXPLANE or sizeof(plchr)
/ sizeof(*plchr).
(plchr): Change sentinel's pl_name to NULL.
