RFR: 8302667: Improve message format when failing to load symbols or libraries [v2]

[Julian Waters]

> DLL_ERROR4 is a macro expanding to an error message when a failure to load a generic item (shared libraries or an exported symbol from said libraries for example) occurs. "Error: loading:" is not a very pretty message, so this small change results in "Error: Failed to load %s" instead, which looks better and also means the message makes more sense if we want to append a reason behind as well, such as "Error: Failed to load libjvm.so because xxx"

Julian Waters has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'openjdk:master' into patch-6
 - Error: Failed to load

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12596/files
  - new: https://git.openjdk.org/jdk/pull/12596/files/43afc03a..5f4370f8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12596&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12596&range=00-01

  Stats: 4003 lines in 132 files changed: 2148 ins; 635 del; 1220 mod
  Patch: https://git.openjdk.org/jdk/pull/12596.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12596/head:pull/12596

PR: https://git.openjdk.org/jdk/pull/12596