Pascal: extract type

[masatake]

This is mostly based on #2241 submitted by @ntrel.
I adjusted the changes to fit the latest codebase.

[codecov]

Codecov Report

Merging #3212 (37b2ed7) into master (7e06c76) will increase coverage by 0.00%.
The diff coverage is 83.33%.

@@           Coverage Diff           @@
##           master    #3212   +/-   ##
=======================================
  Coverage   84.94%   84.95%           
=======================================
  Files         206      206           
  Lines       49030    49044   +14     
=======================================
+ Hits        41650    41665   +15     
+ Misses       7380     7379    -1     

Impacted Files	Coverage Δ
parsers/pascal.c	91.57% <83.33%> (+1.32%)	⬆️

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[masatake]

These lines are not covered by the test cases.

[masatake]

If more than two types are defined under the type keyword, the change doesn't work.

https://www.gnu-pascal.de/gpc/Type-Declaration.html

     type
       { This side is the }     { That side is the }
       { type declaration }     { type definition  }
     
       Arrayfoo            = array [0 .. 9] of Integer;  { array definition }
       Recordfoo           = record                      { record definition }
                               Bar: Integer;
                             end;
     
            { schema def with discriminants ``x, y: Integer'' }
       SchemaFoo (x, y: Integer) = array [x .. y] of Integer;
       CharSetFoo          = set of Char;              { Def of a set }
       ObjectFoo           = object                    { Def of an object }
                               procedure DoAction;
                               constructor Init;
                               destructor Done;
                             end;
       SubrangeFoo         = -123..456;                { subrange def }
     
       EnumeratedFoo       = (Pope,John,the,Second);   { enum type def }
            { Def of a pointer to another type identifier }
       PInteger            = ^arrayfoo;
            { Def of an alias name for another type identifier }
       IdentityFoo         = Integer;
            { Def of an integer which was initialized by 123 }
       InitializedFoo      = Integer value 123;