RFR: 8263421: Module image file is opened twice during VM startup [v2]

[Harold Seigel]

> Please review this fix for JDK-8263421.  The fix stores the JImageFile* in a static that gets initialized when lookup_vm_options() opens the module image file.  The static JimageFIle* is then used by setup_bootstrap_search_path_impl() when creating the ClassPathImageEntry for the module image file, avoiding having to re-open the module image file.
> 
> This fix moved the creation of the ClassPathImageEntry for the module image file from create_class_path_entry() to setup_bootstrap_search_path_impl() because create_class_path_entry() may try to do this multiple times, but the ClassPathImageEntry for the module image file is only actually created once.
> 
> The fix also removes some unused code related to module image file processing.
> 
> The changes were tested with Mach5 tiers 1 and 2 on Linux, Mac OS, and Windows, and Mach5 tiers 3-
> 5 on Linux x64.
> 
> Thanks, Harold

Harold Seigel has updated the pull request incrementally with one additional commit since the last revision:

  add jimage_non_null(), modify destructor

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3591/files
  - new: https://git.openjdk.java.net/jdk/pull/3591/files/09060479..5341b1ed

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3591&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3591&range=00-01

  Stats: 21 lines in 2 files changed: 8 ins; 8 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3591.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3591/head:pull/3591

PR: https://git.openjdk.java.net/jdk/pull/3591