RFR: JDK-8299396: Remove metaprogramming/removeExtent.hpp [v3]

[Justin King]

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

Justin King has updated the pull request incrementally with one additional commit since the last revision:

  Switch to std::remove_extent_t and using instead of typedef
  
  Signed-off-by: Justin King <jcking at google.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11798/files
  - new: https://git.openjdk.org/jdk/pull/11798/files/8693abb1..adf841ae

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11798&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11798&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/11798.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11798/head:pull/11798

PR: https://git.openjdk.org/jdk/pull/11798