RFR: 8255338: CodeSections are never frozen [v2]

[Claes Redestad]

> CodeSections are never actually frozen, so code for freezing can be removed along with some assertions and guarantees.
> 
> A few other minor cleanups, too.

Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:

  Remove insts_limit() and clear_insts_mark(), too

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/834/files
  - new: https://git.openjdk.java.net/jdk/pull/834/files/37aca0c2..dfb19e95

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=834&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=834&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/834.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/834/head:pull/834

PR: https://git.openjdk.java.net/jdk/pull/834