CSegId: Make constexpr capable

Allows the class to be used within constexpr contexts, given it's such a
small class.

Runtime/Character/CSegId.hpp

@@ -3,26 +3,24 @@
 #include "Runtime/IOStreams.hpp"
 #include "Runtime/RetroTypes.hpp"
 
-#include <zeus/CVector3f.hpp>
-
 namespace urde {
 
 class CSegId {
   u8 x0_segId = 0xff;
 
 public:
-  CSegId() = default;
-  CSegId(u8 id) : x0_segId(id) {}
-  CSegId(CInputStream& in) : x0_segId(in.readUint32Big()) {}
-  CSegId& operator++() {
+  constexpr CSegId() noexcept = default;
+  constexpr CSegId(u8 id) noexcept : x0_segId(id) {}
+  explicit CSegId(CInputStream& in) : x0_segId(in.readUint32Big()) {}
+  constexpr CSegId& operator++() noexcept {
     ++x0_segId;
     return *this;
   }
-  CSegId& operator--() {
+  constexpr CSegId& operator--() noexcept {
     --x0_segId;
     return *this;
   }
-  operator u8() const { return x0_segId; }
+  constexpr operator u8() const noexcept { return x0_segId; }
 };
 
 } // namespace urde