RFR: 8253219: Epsilon: clean up unnecessary includes [v2]

[Aleksey Shipilev]

> Static analysis shows a few #include statements in gc/epsilon that are not needed.
> 
> Testing: Linux x86_64 {release, fastdebug, slowdebug} x {+PCH, -PCH}

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Reinstate allocation.hpp include

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/198/files
  - new: https://git.openjdk.java.net/jdk/pull/198/files/f6db93d1..fb49b3de

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=198&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=198&range=00-01

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/198.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/198/head:pull/198

PR: https://git.openjdk.java.net/jdk/pull/198