Never compile scripts as lightweight functions.
Revert "Handle js_tostring on objects without toString or toValue methods."

This reverts commit 7b37ef2b8ad907a3803c5dcc8b184f788f961b80.
Fix boolean equality tests.
Compile pre/post increment/decrement as special opcodes.

They always do addition, never concatenation as strings, so we can't
treat "++a" the same as "a += 1".
Improve jsV_stringtonumber.

Tolerate leading and trailing whitespace, and hexadecimals.
Return NAN if there is trailing garbage or errors.