Move C runtime to new parsing machine design

[orlandohill]

Based on the in-progress Java version? Also see the new JavaScript version.

[glebm]

Would be nice if the AST substrings are slices into the original string (char *, size_t), to improve memory-usage and performance.

[orlandohill]

Yes, makes sense.

Would the idea be to change AST_CHAR to AST_SPLICE, or to add AST_SPLICE as a new type? Something else entirely?

[glebm]

Yes, something like that.

Something like AST_CHARS, containing a string_view (naming matches C++
std::string_view, alternative name: chars_view):

typedef struct _string_view {
  // Does not own the pointer
  char *pointer;
  size_t size;
} string_view;

Ideas for naming:

• AST_CHARS_SLICE
• AST_STRING_SLICE
• AST_CHARS

The AST_CHAR type would then be removed.

[orlandohill]

Sounds good. AST_CHARS seems suitably short and descriptive.