MQTT: add JSON payload corresponding to IEC Structured types

- uses https://github.com/cesanta/frozen
- frozen.c is added as a resulting c file in generat_C (fix toolchain_gcc.py as it was breaking dependency checking)
- structured types are converted to C #define, in turn generating json_scanf and json_printf statements

     1

[TOPOLOGY]

     2

NetName=None

     3

Nodes=0x01

     4

Node64Present=0x01

     5

Node64Name=micromod

     6

Node64DCFName=PEAK MicroMod.eds

     7

EDSBaseName=eds