Revert "make sure we have IO::WaitReadable and IO::WaitWritable with 1.8 mode"

and uses getConstantAt instead of getConstant

This reverts commit df111b759538281e33a7d6b18bfe95f97c7f3029.

Conflicts:
	ext/openssl/src/main/java/org/jruby/ext/openssl/SSL.java

[skip ci]