RFR: 8257985: count_trailing_zeros doesn't handle 64-bit values on 32-bit JVM

[Claes Redestad]

Re-implement count_trailing_zeros as a template function similar to count_leading_zeros, adding support for 8 and 16 bit types as well as for 64-bit types on 32-bit builds, which is currently not supported. This prohibits implementing the log2i_exact proposed by #1663 using count_trailing_zeros, as suggested during review.

Compared to count_leading_zeros the implementation can be slightly simpler since subword specializations can simply use the internal 32-bit variant.

Windows doesn't define _BitScanForward64 on 32-bit targets, so the 32-bit variant for handling 64-bit values becomes more convoluted.

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Commit messages:
 - Fix malformed Windows code
 - Merge branch 'master' into ctz_template
 - Add support for 8 and 16-bit types, refactor tests to test all types
 - 8257985: count_trailing_zeros doesn't handle 64-bit values on 32-bit JVM

Changes: https://git.openjdk.java.net/jdk/pull/1747/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1747&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257985
  Stats: 102 lines in 2 files changed: 72 ins; 0 del; 30 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1747.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1747/head:pull/1747

PR: https://git.openjdk.java.net/jdk/pull/1747