all: assorted cleanups and updates

Changes include:
  - add a bunch of "noexcept", mostly to operators and forceinline
  - use "uchar"
  - use "charptr"
  - rename options_t to Options
  - add ptr_check_no_overlap()
  - rewrite p_exe.cpp, NFCI
  - clang-format help.cpp
  - spelling fixes

src/ui.h

@@ -39,7 +39,7 @@ public:
     UiPacker(const Packer *p_);
 
 public:
-    virtual ~UiPacker();
+    virtual ~UiPacker() noexcept;
 
     static void uiConfirmUpdate();
     static void uiPackTotal();