See ticket [6efa4f571af052].

Reworked the Json/C code to use a bison-pased parser provided by Mikhail.
No separate data structures to convert, just direct generation of Tcl structures.
Changes compared to the original submission:

- Use List, not Dict operations for objects, i.e. be Tcl 8.4 compatible.

- Do not generate Int/Double objects, only strings.
  Conversion to actual int is lazy, when actually needed.
  Also ensures that compile-time Tcl version does not
  restrict range of integers, only runtime Tcl version.

- Allow all values as toplevel json, not just array and object.

- Currently no shared objects for the fixed values (null, true, false).

Note that the RE-based json validation is still faster on even
moderatly sized strings, even when just using a stripped C lexer not
generating token values.

Bumped jsonc to version 1.1 and tcllibc to version 0.3.12.