RFR: 8294591: Fix cast-function-type warning in TemplateTable

[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:

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/10493/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10493&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294591
  Stats: 44 lines in 10 files changed: 9 ins; 0 del; 35 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