RFR: 8257743: Minimal build on AArch64 failed with --disable-precompiled-headers

[Hao Sun]

The build failed due to undeclared 'java_lang_ref_Reference'.
Making the corresponding header (classfile/javaClasses.hpp) included would fix it.

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Commit messages:
 - 8257743: Minimal build on AArch64 failed with --disable-precompiled-headers

Changes: https://git.openjdk.java.net/jdk/pull/1619/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1619&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257743
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1619.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1619/head:pull/1619

PR: https://git.openjdk.java.net/jdk/pull/1619