Added readln() function in std/io.cc.
Added readln() function in std/io.cc.

felipensp/clever,clever-lang/clever,clever-lang/clever,felipensp/clever,felipensp/clever,clever-lang/clever,clever-lang/clever,clever-lang/clever,felipensp/clever,felipensp/clever,clever-lang/clever,felipensp/clever,felipensp/clever,clever-lang/clever