added checks for code generator and error markers. At last!
Should have done this a loooonngggg time ago, as even I got puzzled
sometimes when no files would be generated because I had not set up a
code generator!
added createTypeString method to IrFactory with size parameter
added automatic cast of string expressions into integers
(this is only done for strings contained in other expressions, never for
print statements)
removed obsolete TypeEvaluator at last
added casts for any operator when both operands are integers
best solution would be constant folding
updated VHDL implementation of single-port/dual-port RAM
need to add true dual-port (and rename existing to pseudo dual port)