[foreign-abi] RFR: 8239345: need an enum for standard C types and a way to get a memory layout for those C types

[Athijegannathan Sundararajan]

SystemABI.Type enum added and ABI_CLASS attribute of layout removed (inferred from Type instead)

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Commits:
 - 27ab6505: 8239345: need an enum for standard C types and a way to get a memory layout for those C types

Changes: https://git.openjdk.java.net/panama-foreign/pull/24/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/24/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8239345
  Stats: 365 lines in 14 files changed: 253 ins; 50 del; 62 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/24.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/24/head:pull/24

PR: https://git.openjdk.java.net/panama-foreign/pull/24