RFR: 8259287: AbstractCompiler marks const in wrong position for is_c1/is_c2/is_jvmci

[Xin Liu]

I think the intention is to have constant member functions.

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Commit messages:
 - 8259287: AbstractCompiler marks const in wrong position for is_c1/is_c2/is_jvmci

Changes: https://git.openjdk.java.net/jdk/pull/1953/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1953&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259287
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1953.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1953/head:pull/1953

PR: https://git.openjdk.java.net/jdk/pull/1953