Add support for Abstraction data types in enter_block()

[yimjay]

Define a new block to specify Abstraction data types and configure enter_block() to recognize the block.

[yimjay]

Added support for a block itself in last commit pushed on 8/12.

• Added case MAP : newtab = block; to XFORM.enter_block() in analysis.pt

Tested by running the following:

testMap = MAP{"a" => 1,
                "b" => 2,
                "c" => 3};
XFORM.enter_block(testMap);
DEBUG{GLOBAL.SymTable};
XFORM.exit_block(testMap);

where output was:

DEBUGGING at level 1
END DEBUGGING at level 1
DEBUGGING result: SymTable===>POETList:(MAP{"a"=>1;"b"=>2;"c"=>3;})