RFR: JDK-8264191: Javadoc search is broken in Internet Explorer

[Hannes Wallnöfer]

The RegExp `flags` property is replaced with the much better supported `ignoreCase` property in this change.

https://caniuse.com/mdn-javascript_builtins_regexp_flags
https://caniuse.com/mdn-javascript_builtins_regexp_ignorecase

We don't have automated tests for the search script on browsers. I have tested the change by running `test/langtools/jdk/javadoc/doclet/testSearchScript/TestSearchScript.java` with GraalJS as well as doing manual testing with current Firefox, Safari, Chrome as well as IE 11 and Edge 44.

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Commit messages:
 - JDK-8264191: Javadoc search is broken in Internet Explorer

Changes: https://git.openjdk.java.net/jdk/pull/3202/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3202&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264191
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3202.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3202/head:pull/3202

PR: https://git.openjdk.java.net/jdk/pull/3202