RFR: 8294591: Fix cast-function-type warning in TemplateTable [v3]

[Aleksey Shipilev]

> After [JDK-8294314](https://bugs.openjdk.org/browse/JDK-8294314), we would have `templateTable.cpp` excluded with cast-function-type warning. The underlying cause for it is casting functions for `ldc` bytecodes, which take `bool`-typed handlers:

Aleksey Shipilev 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 branch 'master' into JDK-8294591-warning-cast-function-type-templatetable
 - Also disable warnings in gtests
 - Fix

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Changes: https://git.openjdk.org/jdk/pull/10493/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10493&range=02
  Stats: 41 lines in 10 files changed: 6 ins; 1 del; 34 mod
  Patch: https://git.openjdk.org/jdk/pull/10493.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10493/head:pull/10493

PR: https://git.openjdk.org/jdk/pull/10493