Add compound assignment

[yodalee]

Add support to compound assignment +=, -=, *=. However, single line with multiple compound assignment to same variable will not work in this implementation. like: a += a += 10;

[jserv]

Fix CI failure and append test cases.

[yodalee]

It is interesting that I cannot reproduce the error on my computer. I think I need more time to investigate it. The expression a += a += 10 is perfectly legal according to standard. Though it is stupid to write like that. I think we can ignore it. It is still possible to implement it by adding some new opcode I think.

[yodalee]

Oh great. I update to upstream and I can reproduce the error now.

[jserv]

@yodalee, why would you like to introduce new opcodes? And, how do the proposed opcode look like?

[yodalee]

Update to solve the regression fail. The reason is actually stupid: amacc currently require variable declaration appears before statement.

[jserv]

The reason is actually stupid: amacc currently require variable declaration appears before statement.

Issue #36 aims to resolve such known restriction.

[jserv]

@yodalee, Please append new test cases as well.

[yodalee]

Update some tiny test to compound assign. About the new opcode to solve the expression a += a += 10. I think I need some time to consider about it.

[yodalee]

Updated.

[yodalee]

Thanks @jserv