Support unary operators

[paulfryzel]

http://www.ecma-international.org/ecma-262/5.1/#sec-11.4

• 11.4.1 delete (Delete property #12)
• 11.4.2 void
• 11.4.3 typeof
• 11.4.4 ++
• 11.4.5 --
• 11.4.6 +
• 11.4.7 -
• 11.4.8 ~
• 11.4.9 !

tests: test262/11.4

[paulfryzel]

• 11.4.7 - (SMI only) (paulfryzel@1c5af67)