Use Registry on Windows to store preferences

No change at all to non-Windows builds.

Everything seems to work with preferences - but only tested on Win7

Remaining issue: displaying an icon (or the logo in the About dialog)

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

dive.h

@@ -187,6 +187,10 @@ struct dive {
  * the input and output may come in some random format. This
  * keeps track of those units.
  */
+/* turns out in Win32 PASCAL is defined as a calling convention */
+#ifdef WIN32
+#undef PASCAL
+#endif
 struct units {
 	enum { METERS, FEET } length;
 	enum { LITER, CUFT } volume;