Fix #399: ArrayIndexOutOfBounds inside soot

Its investigation in context of issue #399. Soot was crashing on big class files with exception:

java.lang.ArrayIndexOutOfBoundsException: -29458 at soot.coffi.CFG.processCPEntry(CFG.java:2652)

Investigation shown following byte code that Soot was trying to parse:

Code: stack=4, locals=0, args_size=0 0: ldc2_w #36078 // double 0.017453292519943295d

Easy check in hex presentation (-29458=0xFFFF8CEE and 36078=0x8CEE) shows that its classical signed/unsigned misstake.
Root case was in Instruction_intindex where argument (the index) was read as singed short which was ok till the value fit positive boundary of short, but turned into negative value once overflows. This class is super class for following set of Java bytecode which were affected as well (corresponding to JVM spec):

• anewarray
• checkcast
• getfield
• getstatic
• instanceof
• invokedynamic
• invokeinterface
• invokenonvirtual
• invokestatic
• invokevirtual
• ldc2
• ldc2w
• multianewarray
• new
• putfield
• putstatic

Fix is trivial: read value as unsigned short

NP: this bug was hidding from very beginning and was just waiting big enough class file to detonate.