RFR: 8331020: Assign LANG to C++ for Windows code that uses C++

[Julian Waters]

Currently, on Windows LANG is not assigned to C++ for some code that does use C++. This just works because link.exe does not bother about what kind of code it is currently linking. gcc however, does. It doesn't hurt to assign LANG to C++ as a formality in such cases, which this changeset does. This also renames LINK_TYPE to LANG, which the original change to remove the TOOLCHAIN parameter used to do

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Commit messages:
 - Assign LANG to C++ in Lib.gmk
 - Assign LANG to C++ in Lib.gmk
 - Assign LANG to C++ in Launcher.gmk
 - Assign LANG to C++ in Lib.gmk
 - Assign LANG to C++ in AwtLibraries.gmk
 - Rename import in Lib.gmk
 - Rename ClientLibraries.gmk to 2dLibraries.gmk
 - LINK_TYPE to LANG in ClientLibraries.gmk
 - LINK_TYPE to LANG in JdkNativeCompilation.gmk
 - Add C++ to Windows in Lib.gmk
 - ... and 11 more: https://git.openjdk.org/jdk/compare/7a895552...8d0701bd

Changes: https://git.openjdk.org/jdk/pull/18927/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18927&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331020
  Stats: 52 lines in 19 files changed: 15 ins; 3 del; 34 mod
  Patch: https://git.openjdk.org/jdk/pull/18927.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18927/head:pull/18927

PR: https://git.openjdk.org/jdk/pull/18927