Add filter for Kotlin when-expressions with String

[Godin]

No description provided.

[marchof]

@Godin Would prefer to review this after #735 is merged to master.

[Godin]

@marchof rebased

Currently diff between StringSwitchEcjFilter and KotlinWhenStringFilter is

26,27c26,27
<  * Filters code that is generated by ECJ for a <code>switch</code> statement
<  * with a <code>String</code>.
---
>  * Filters bytecode that Kotlin compiler generates for <code>when</code>
>  * expressions with a <code>String</code>.
29c29
< public final class StringSwitchEcjFilter implements IFilter {
---
> public final class KotlinWhenStringFilter implements IFilter {
46a47
> 			nextIsVar(Opcodes.ALOAD, "s");
73a75,77
> 					// jump to next comparison or default case
> 					nextIs(Opcodes.IFEQ);
> 					final JumpInsnNode jump = (JumpInsnNode) cursor;
75c79
< 					nextIs(Opcodes.IFNE);
---
> 					nextIs(Opcodes.GOTO);
83c87
< 					if (cursor.getNext().getOpcode() == Opcodes.GOTO) {
---
> 					if (jump.label == defaultLabel) {
85,86d88
< 						// jump to default
< 						nextIs(Opcodes.GOTO);

😆 but I'd like to propose and would really prefer to work on refactoring separately.

[marchof]

Idea: Make a variant of skipNonOpcodes in base class public:

private static AbstractInsnNode skipNonOpcodes(AbstractInsnNode start)

[marchof]

@Godin Do you want me to merge it as is or do you like to pick-up the skipNonOpcodes idea before?

[Godin]

@marchof A quick random thought: instructionAfterLabel(LabelNode) compared to skipNonOpcodes(AbstractInsnNode) is safer since accepts only LabelNode. So let's go without skipNonOpcodes - will think about this at a time of thinking about similarity between StringSwitchEcjFilter and KotlinWhenStringFilter.

[marchof]

👍 Let's wait for Travis.