Update pom.xml to specify that test code is Java 8

To get the test case JvstTest4.testMethodParameters() to work
the <testSource> and <testTarget> elements are set to "1.8"
and the compiler argument "-parameters" is added.
Fix JASSIST-220

Static methods on interfaces in Java 8 means
that the INVOKESTATIC opcode can sometimes refer
to an item that is an InterfaceMethodrefInfo
(instead of a MethodrefInfo).

This is now handled in the
ConstPool.getMethodref...() methods by casting
to MemberrefInfo instead (since MemberrefInfo
contains all the needed information).
Merge pull request #11 from jkaving/JASSIST-220

Fix for JASSIST-220
removed unused import declarations
fixed JIRA-227
fixed JASSIST-230
fixed a bug of accesses to annotation arguments.
If foo.Bar.Baz is a nested class in foo.Bar, then the argument of
@MyAnnotation(foo.bar.Baz.class) could not be obtained.
The test code is javassist.JvstTest4#testAnnArg().
fixed a bug of accesses to annotation arguments (cont.).
did minor refactoring.
Support Javaflow NEW bytecode pattern for replacement.
Merge pull request #21 from baron1405/javaflow

JASSIST-234.  Support Javaflow NEW bytecode pattern for replacement.
logged the fix of JIRA JASSIST-234.