feat+fix: make compiler STRONGAAA

- FEAT: add source code length field in `fzl_reader_t` struct
- FIX: check name, lpair (lparen) and rpair (rparen) when lexing call
- FIX: check string literal termination
- FIX: increment position even on empty string to prevent infinite
lexing loop
- FIX: add string terminator in `fzl_mktoken` when allocating space for
string value
- FIX: add check for errors in recursevly called `walk`
- FIX: change source code holder from stack-stored `char[8192]` to
dynamically allocated with actual file size holder
- FIX: correct constant hasing util to hash actual string value instead
of link

include/compiler/fzl_reader.h

@@ -20,6 +20,7 @@ typedef struct
   fzl_reader_ll_t *last;
 
   char *source;
+  size_t size;
   size_t position;
   bool at_end;
 } fzl_reader_t;