This patch implements the core part of let/const statements. Redeclarations are correctly
detected and separate contexts are correctly created for these statements. Register
optimizations are also emplyed whenever possible.
Lots of features are still missing:
- checking the var statements in eval
- const are treated as lets
- single statement checks are missing
- export declarations are exported as vars, let/const export is not supported
JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com