[Bug fix]return incorrect nullness in the method Scene#getTypeUnsafe

[canliture]

fixed #1647
fixed #1696

In method soot.jimple.toolkits.callgraph.OnFlyCallGraphBuilder#addType, it calls Scene#getTypeUnsafe(String),
but the argument passed into the method Scene#getTypeUnsafe(String) may be quoted, just like:

"sun.reflect.'annotation'.AnnotationType"

"java.lang.'annotation'.Annotation"

Scene#getTypeUnsafe(String) will return null if the argument passed into is quoted, it will lead to Soot crashing with NullPointerException or IllegalArgumentException somewhere, just like the following 'test3' failing to pass the test with IllegalArgumentException

Here is a minimal test for evaluating the bug fixing.

public class SootResolverTest {
    @Test
    public void test3() {
        G.reset();

        Options.v().set_whole_program(true);

        Scene.v().loadNecessaryClasses();

        /* returnType maybe be null in SootMethodRefImpl's constructor, resulting in throwing IllegalArgumentException */
        PackManager.v().runPacks();
    }
}

Before fixing the bug, soot will crash with the messages:

java.lang.IllegalArgumentException: Attempt to create SootMethodRef with null returnType

	at soot.SootMethodRefImpl.(SootMethodRefImpl.java:86)
	at soot.Scene.makeMethodRef(Scene.java:1962)
	at soot.jimple.toolkits.callgraph.OnFlyCallGraphBuilder.addType(OnFlyCallGraphBuilder.java:608)
	at soot.jimple.toolkits.callgraph.CallGraphBuilder.processReceivers(CallGraphBuilder.java:201)
	at soot.jimple.toolkits.callgraph.CallGraphBuilder.process(CallGraphBuilder.java:128)
	at soot.jimple.toolkits.callgraph.CallGraphBuilder.build(CallGraphBuilder.java:114)
	at soot.jimple.toolkits.callgraph.CHATransformer.internalTransform(CHATransformer.java:54)
	at soot.SceneTransformer.transform(SceneTransformer.java:36)
	at soot.Transform.apply(Transform.java:105)
	at soot.RadioScenePack.internalApply(RadioScenePack.java:64)
	at soot.jimple.toolkits.callgraph.CallGraphPack.internalApply(CallGraphPack.java:61)
	at soot.Pack.apply(Pack.java:118)
	at soot.PackManager.runWholeProgramPacks(PackManager.java:619)
	at soot.PackManager.runPacksNormally(PackManager.java:500)
	at soot.PackManager.runPacks(PackManager.java:425)
        ... ...
        ... ...

Why type name string may be quoted?(like sun.reflect.'annotation'.AnnotationType)
For serialization, e.g. to .jimple format, a textual (and quoted as needed) representation of type is necessary.So for some reserved names, they will be replaced with quoted.(reserved names table are listed in the method Scene#setReservedNames)

"annotation" is a reserved name for textual serialization, and in the method Scene#quotedNameOf, If a part of a string contains reserved name, the part will be replaced with 'part', just like annotation replaced with 'annotation'.