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.

rogueviz/newconf.cpp

@@ -4,14 +4,7 @@
 
 #include "../hyper.h"
 
-#ifndef CAP_NCONF
-#define CAP_NCONF 0
-#endif
-
 #if CAP_NCONF
-#ifndef CAP_DRAW
-#define CAP_DRAW 0
-#endif
 #define main nconf_main
 #undef unordered_map
 #undef self