RFR: 8287171: Refactor null caller tests to a single directory [v5]

[Tim Prinzing]

> Created a test at test/jdk/jdk/nullCaller called NullCallerTest that creates a test module with some resources in it for the actual tests that occur at the native level. The native part was switched to c++ instead of c to make it easier to create helper objects that reduce the redundant code performing error checking. The two helper classes InstanceCall and StaticCall were placed in an include file called CallHelper.hpp. The main part of the tests are in exeNullCallerTest.cpp, and there is a separate function for each of the bug reports.

Tim Prinzing has updated the pull request incrementally with one additional commit since the last revision:

  improve comment

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8934/files
  - new: https://git.openjdk.java.net/jdk/pull/8934/files/7eb5dbcb..777c4f5f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8934&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8934&range=03-04

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8934.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8934/head:pull/8934

PR: https://git.openjdk.java.net/jdk/pull/8934