C4819 warnings on Windows

[Yasumasa Suenaga]

Hi all,

I tried to build OpenJDK on WSL (Windows 10 1809 + VS2017 (15.9.4) + Ubuntu 
18.04 LTS).
However, I saw some C4819 warnings as below:

```
c:/OpenJDK/jdk/src/hotspot/share/compiler/methodMatcher.cpp(258): warning 
C4819: ファイルは、現在のコード ページ (0) で表示できない文字を含んでいます。データの損失を防ぐために、ファイルを Unicode 
形式で保存してください。
```

* The locale of my laptop is set to Japanese (CP932), thanks :-)


I saw this warning at 3 files as below:

  1. hotspot/share/code/codeHeapState.cpp
  2. java.desktop/share/native/libfreetype/src/autofit/afscript.h
  3. hotspot/share/compiler/methodMatcher.cpp

We can see the problem in 1. and 2. with iconv:
  $ iconv -f US-ASCII -t UTF8 <file>


I've fixed them with following patch. It works fine on my environment:
  http://cr.openjdk.java.net/~ysuenaga/wsl/build-warnings/

I think we should fix them, but I don't know what component/subcomponent should 
we set to JBS.
Could you help?


Thanks,

Yasumasa