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.cpp

@@ -182,7 +182,7 @@ UiPacker::UiPacker(const Packer *p_) : ui_pass(0), ui_total_passes(0), p(p_), s(
         s->mode = M_CB_SCREEN;
 }
 
-UiPacker::~UiPacker() {
+UiPacker::~UiPacker() noexcept {
     cb.reset();
     delete s;
     s = nullptr;