Implement delete operator in the vm

[raskad]

It changes the following:

• Implements the delete operator in the vm
• Remove unneeded syntax error in delete operator execution

[raskad]

Fixed one test for the tree walking interpreter but that should not really be the focus.

Test262 conformance changes:

Test result	main count	PR count	difference
Total	86,438	86,438	0
Passed	37,456	37,458	+2
Ignored	19,022	19,022	0
Failed	29,960	29,958	-2
Panics	0	0	0
Conformance	43.33%	43.34%	+0.00%

Fixed tests (2):

test/language/global-code/S10.1.7_A1_T1.js [strict mode] (previously Failed)
test/language/global-code/S10.1.7_A1_T1.js (previously Failed)

[jedel1043]

Looks good!