Move all defaulting-of-CAP_FOO to sysconfig.h.

- The phrase `#ifdef CAP_` should never appear anywhere.

- The phrase `#ifndef CAP_` should appear only in sysconfig.h.

- The phrases `#if CAP_` and `#if !CAP_` may appear wherever,
    as long as "sysconfig.h" is included first.

The rules for `CAP_FOO` equally apply to `ISFOO`.

There are many one-off macros still tested with `#ifdef`,
including `HAVE_ACHIEVEMENTS`, `PRINT_ACHIEVEMENTS`,
`FAKEWEB`, `FAKE_SDL`, `EASY`, and `WHATEVER`. I don't
have much grasp on what these are used for or how they're
configured, so I'm leaving them alone.

surface.cpp

@@ -370,10 +370,6 @@ int dexp_comb_colors[16] = {
 int coverage_style;
 EX vector<pair<hyperpoint, int> > coverage;
 
-#ifndef CAP_KUEN_MAP
-#define CAP_KUEN_MAP 0
-#endif
-
 #if CAP_KUEN_MAP
 void draw_kuen_map() {
   SDL_Surface *kuen_map = SDL_CreateRGBSurface(SDL_SWSURFACE,512,512,32,0,0,0,0);