RFR: JDK-8299482: Remove metaprogramming/isIntegral.hpp [v3]

[Justin King]

> Code cleanup of pre-C++11 <type_traits> implementations.

Justin King has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:

 - Merge remote-tracking branch 'upstream/master' into remove-is-integral
 - Add missing include
   
   Signed-off-by: Justin King <jcking at google.com>
 - Remove metaprogramming/isIntegral.hpp
   
   Signed-off-by: Justin King <jcking at google.com>

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Changes: https://git.openjdk.org/jdk/pull/11818/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11818&range=02
  Stats: 82 lines in 4 files changed: 3 ins; 65 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/11818.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11818/head:pull/11818

PR: https://git.openjdk.org/jdk/pull/11818