Update StringBuilderRunOnGpu4 test case

Hello Phil,
please can you help me to fix this *StringBuilderRunOnGpu4* test case?
The GPU memory is somehow malformed by the *StringBuilder*.
I hope we can fix this issue soon.
Thanks!
Martin

```
$ java -Xmx8g -jar Rootbeer.jar -runtest org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderTest4
caching package names for: /home/martin/workspace/rootbeer2/Rootbeer.jar
caching package names for: /usr/local/java/jdk1.6.0_45/jre/lib/rt.jar
remapping class: java.util.concurrent.atomic.AtomicLong
remapping class: org.trifort.rootbeer.testcases.rootbeertest.remaptest.CallsPrivateMethod
building class hierarchy...
caching virtual methods...
finding entry points...
loading follows strings...
loading to_signatures strings...
entry point: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>
loading forward string call graph for: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>...
remapping: org/trifort/rootbeer/remap/GpuAtomicLong to java/util/concurrent/atomic/AtomicLong
loading reverse string call graph for: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>...
remapping: org/trifort/rootbeer/remap/DoesntCallPrivateMethod to org/trifort/rootbeer/testcases/rootbeertest/remaptest/CallsPrivateMethod
entry point: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>
loading forward string call graph for: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>...
loading reverse string call graph for: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>...
entry point: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>
loading forward string call graph for: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>...
loading reverse string call graph for: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>...
building array types...
numbering types...
loading scene...
finding hierarchy classes reachable from dfs walk...
creating empty classes according to type number...
filling in outer classes...
collecting fields for classes and adding to declaring class...
adding empty methods...
adding method bodies...
Total loaded classes: 1516
Total loaded methods: 4782
getEntryPoints: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>
running transform2 on: <org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderRunOnGpu4: void gpuMethod()>...
compiling CUDA code for 32bit and 64bit...
generating serialization bytecode...
added interface CompiledKernel
writing classes out...
Packing up to: output.jar
[TEST 1/1] org.trifort.rootbeer.testcases.rootbeertest.serialization.StringBuilderTest4@344d6527
init big_array: double[16500][1000]
init big_array: double[16500][1000]
  0: ac 00 00 00 00 00 00 00 76 00 00 00 91 00 00 00 
 16: ff ff ff ff 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: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
144: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
160: 01 00 00 00 9c 0d 00 00 30 00 00 00 00 00 00 00 
176: ff ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 
192: 0d 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
208: 01 00 00 00 4a 0b 00 00 30 00 00 00 00 00 00 00 
224: ff ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 
240: 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
java.lang.RuntimeException: address out of range: 2121593344
	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:280)
	at org.trifort.rootbeer.runtime.CUDAContext.run(CUDAContext.java:186)
	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:57)
	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
```