Simplify boolean literal mutators
Port if node mutator to parser
Port if node mutator to parser
Port literal array mutator to parser
Port literal fixnum emitter to parser
Port literal float emitter to parser

Also simplify emitter for special float cases Nan, Inf, -Inf
Port literal hash emitter to parser
Fix literal nil mutator specs
Add fixnum scalar bounds mutation for literal fixnu,s

Closes #23