RFR: JDK-8304684: Memory leak in DirectivesParser::set_option_flag [v3]

[Justin King]

> Add missing `FREE_C_HEAP_ARRAY` call.

Justin King has updated the pull request incrementally with four additional commits since the last revision:

 - Make directives enum macros more fool proof
   
   Signed-off-by: Justin King <jcking at google.com>
 - Fix capitalization
   
   Signed-off-by: Justin King <jcking at google.com>
 - Fix unqualified member variable reference
   
   Signed-off-by: Justin King <jcking at google.com>
 - Update DirectiveSet to take ownership of string options
   
   Signed-off-by: Justin King <jcking at google.com>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13125/files
  - new: https://git.openjdk.org/jdk/pull/13125/files/a832d587..7ddd0cec

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13125&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13125&range=01-02

  Stats: 95 lines in 3 files changed: 64 ins; 14 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/13125.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13125/head:pull/13125

PR: https://git.openjdk.org/jdk/pull/13125