* DSNLEXER now owns an abstract LINE_READER by pointer so that polymorphism
can be used in alternative LINE_READERS.
* Write FILE_LINE_READER and STRING_LINE_READER. The latter can be used
to parse text coming from the clipboard or other string source.
constructor takes a keyword table, so it can be used for arbitrary DSN
syntax files of your own chosing. Simply create an enum {} with all your
unique tokens in it. Then create a KEYWORD table. See SPECCTRA_DB::keywords[].
The reason you want an enum is to give the C++ debugger better type information
so it can show symbolic integer symbols.
* Factored out common richio.cpp and richio.h
which is what DSNLEXER uses.
* Fixed some minor issues with reading circuit descriptor from a *.dsn file.
dickelbeck