Unwrap PHP objects when passing them back from JavaScript to PHP.
Don't rethrow outer exception if report_uncaught is false.

This would cause the exception to stick around and the next time JavaScript
is executed, this exception would be (anomalously) thrown.
Cleanup: remove some warnings when compiled with -Wunused
Clean up allocation/deallocation of php_v8js_ctx.

Use the constructor and destructor functions (don't just cross our fingers
and hope that zeroing out memory will work).
Handle NULL in global.var_dump().
Bug fixes for JavaScript var_dump implementation (make it match PHP).
Add isolate parameter to V8JS_* macros.

This avoids unnecessary calls to Isolate::GetCurrent() in the implementation.
By standardizing on the V8JS_SYM and V8JS_STR macros we also standardize on
UTF-8 encoding for v8 strings.
Merge pull request #61 from cscott/misc-cleanup

A week's worth of cleanup