feat: Type-dependent Haskell code generation

Caveat: type is still not being assigned for the Sequence()
  constructor.

  Also fixes the parsing of literal strings (whitespace just after
  the opening quote was being ignored, and was ambiguous just
  before the opening quote).

tests/basic.spt

@@ -1,15 +1,15 @@
 module basic
 language fostr
 
-
 test hw1_type [[
-[[stream]] << [['Hello,	world!']]
+[[stream]] << [['Hello,	world! ']] << [[3+2]] << ' times.'
 ]]
 run get-type on #1 to STREAM()
 run get-type on #2 to STRING()
+run get-type on #3 to INT()
 run get-type to STREAM()
 /** writes
-Hello,	world!**/
+Hello,	world! 5 times.**/
 
 /** md
 Title: A whirlwind tour of fostr