Move B_COLOR_WHICH_COUNT to private ServerReadOnlyMemory header.

This means the B_COLOR_WHICH_COUNT goes from being a public constant to a
private one. It sill looks like a public constant starting with a B_ though.
I hope that's not a big deal. Too bad we can't get the count of an enum.

headers/private/app/ServerReadOnlyMemory.h

@@ -13,6 +13,13 @@
 #include <InterfaceDefs.h>
 
 
+// Update this constant with the largest color constant excluding
+// B_SUCCESS_COLOR and B_FAILURE_COLOR.
+// If you add a constant with index greater than 100 you'll have to add
+// to the second operand.
+static const int32 B_COLOR_WHICH_COUNT = B_SCROLL_BAR_THUMB_COLOR + 3;
+
+
 struct server_read_only_memory {
 	rgb_color	colors[B_COLOR_WHICH_COUNT];
 };