Add StringBuilderTest4 test case

Hello Phil,

this pull request includes a *StringBuilderTest4* test case for https://github.com/pcpratts/rootbeer1/issues/154.

```
$ ant clean && ant && ./pack-rootbeer
$ java -Xmx16g -jar Rootbeer.jar -runtest org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderTest4
[TEST 1/1] org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderTest4@5329e7c6
big_array: double[69878][10677]
array2: double[69878]
array2: double[10677]
big_array: double[69878][10677]
array2: double[69878]
array2: double[10677]
  0: ca 00 00 00 00 00 00 00 e1 00 00 00 94 00 00 00 
 16: af 00 00 00 ff ff ff ff ff ff ff ff ff ff ff ff 
 32: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 
 48: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 
 64: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 
 80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 
 96: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 
112: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 
128: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 
144: ff ff ff ff ff ff ff ff 00 00 00 00 00 00 00 00 
160: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
176: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
192: 01 00 00 00 9d 0d 00 00 30 00 00 00 00 00 00 00 
208: ff ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 
224: 0f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
240: 01 00 00 00 49 0b 00 00 30 00 00 00 00 00 00 00 
I will NOT throw java.lang.RuntimeException
java.lang.RuntimeException: address out of range: 2683938i2���
	at org.trifort.rootbeer.runtime.CheckedFixedMemory.setAddress(CheckedFixedMemory.java:20)
	at org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4Serializer.doReadFromHeap(Jasmin)
	at org.trifort.rootbeer.runtime.Serializer.readFromHeap(Serializer.java:155)
	at org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4Serializer.doReadStaticsFromHeap(Jasmin)
	at org.trifort.rootbeer.runtime.Serializer.readStaticsFromHeap(Serializer.java:171)
	at org.trifort.rootbeer.runtime.CUDAContext.readBlocks(CUDAContext.java:278)
	at org.trifort.rootbeer.runtime.CUDAContext.run(CUDAContext.java:184)
	at org.trifort.rootbeer.runtime.Rootbeer.run(Rootbeer.java:105)
	at org.trifort.rootbeer.test.RootbeerTestAgent.test(RootbeerTestAgent.java:195)
	at org.trifort.rootbeer.test.RootbeerTestAgent.testOne(RootbeerTestAgent.java:44)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.trifort.rootbeer.entry.RootbeerTest.runTests(RootbeerTest.java:55)
	at org.trifort.rootbeer.entry.Main.run(Main.java:170)
	at org.trifort.rootbeer.entry.Main.main(Main.java:211)
  FAILED
  Exception thrown at index: 0
```

Thanks!

Martin