RFR: 8259839 SystemDictionary exports too much implementation

[Coleen Phillimore]

I apologize for the large change but it's really a bunch of little cleanups combined made while trying to understand the code.  Only number 8 below changes any behavior.  Tested with tier1-8 (24hr Dacapo is still running).

In systemDictionary.cpp:
 1. moved placeholder table and other table sizes into systemDictionary.cpp
 2. Made SystemDictionary::find_class() into a verification function called verify_dictionary_entry since that's what it was used for 
 3. Moved a resolve_or_fail() down and removed redundant checks before calling handle_resolution_exception
 4. Fixed some comments
 5. child_name confused me. class_name and super_name are more meaningful in these contexts
 6. callers of find_or_define_instance_class had to check for a different klass return (with AllowParallelDefineClass), or an exception in order to deallocate one of the classes, so I wrapped it into a function and renamed find_or_define_instance_class into find_or_define_helper.
 7. find_placeholder() is really used to verify_placeholder(). Actually the verification was a nop. Fixing it found a bug in that CDS was calling define_instance_class rather than find_or_define_instance_class for parallelCapable class loader's that it shares, so verify_placeholder() was failing.  Changed the CDS code to call find_or_define_instance_class instead.

In systemDictionary.hpp, I moved the static data members and moved declarations around to make private and have a single protected block for SystemDictionaryShared to use.

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Commit messages:
 - Fix mergeo
 - 8259839: SystemDictionary exports too much implementation

Changes: https://git.openjdk.java.net/jdk/pull/2247/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2247&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259839
  Stats: 305 lines in 6 files changed: 78 ins; 132 del; 95 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2247.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2247/head:pull/2247

PR: https://git.openjdk.java.net/jdk/pull/2247