Draft language spec for JEP 355: Text Blocks

[Alex Buckley]

Please see 
http://cr.openjdk.java.net/~abuckley/jep355/text-blocks-jls.html for JLS 
changes that align with the JEP.

Text blocks compile to the same class file construct as string literals, 
namely CONSTANT_String_info entries in the constant pool. Helpfully, the 
JVMS is already agnostic about the origin of a CONSTANT_String_info, 
making no reference to "string literals". Therefore, there are no JVMS 
changes for text blocks, save for a tiny clarification w.r.t. annotation 
elements.

Alex