map type not supported by TITAN

Summary

map type is not supported by TITAN.

Steps and/or TTCN-3 code to reproduce

type map integer to string mymap;

What is the current bug behavior?

the map keyword is not accepted, and compilation fails.

What is the expected correct behavior?

a map type should be created, and should be able to be instantiated and used accoring to section 6.2.15 of the TTCN-3 standard

Relevant logs and/or screenshots

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2022-05-12_12:58:51: starting to build address
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sh -c make dep  
/home/lee/git/titan.core/Install/bin/compiler  \
../src/maptest.ttcn ../src/subtypes.ttcn  - ../src/maptest.ttcn ../src/subtypes.ttcn
Notify: Parsing TTCN-3 module `../src/maptest.ttcn'...
../src/maptest.ttcn:3.6-8: error: at or before token `map': syntax error
Notify: Parsing TTCN-3 module `../src/subtypes.ttcn'...
Notify: Error found in the input modules. Code will not be generated.
make: *** [Makefile:154: compile] Error 1
Operation failed with return value: 2

Possible fixes

Titan version

8.1.0

Platform details (OS type and version)

Microsoft Windows 10 Enterprise 10.0.19042

/cc @aknappqwt