RFR: 8289834: Add SBCS and DBCS Only EBCDIC charsets

[Ichiroh Takiguchi]

OpenJDK supports "Japanese EBCDIC - Katakana" and "Korean EBCDIC" SBCS and DBCS Only charsets.
|Charset|Mix|SBCS|DBCS|
| -- | -- | -- | -- |
| Japanese EBCDIC - Katakana | Cp930 | Cp290 | Cp300 |
| Korean | Cp933 | Cp833 | Cp834 |

But OpenJDK does not supports some of "Japanese EBCDIC - English" / "Simplified Chinese EBCDIC" / "Traditional Chinese EBCDIC" SBCS and DBCS Only charsets.

I'd like to request Cp1027/Cp835/Cp836/Cp837 for consistency
|Charset|Mix|SBCS|DBCS|
| ------------- | ------------- | ------------- | ------------- |
| Japanese EBCDIC - English | Cp939 | **Cp1027** | Cp300 |
| Simplified Chinese EBCDIC | Cp935 | **Cp836** | **Cp837** |
| Traditional Chinese EBCDIC | Cp937 | (*1) | **Cp835** | 

*1: Cp037 compatible

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

Commit messages:
 - 8289834: Missing SBCS and DBCS Only EBCDIC charsets

Changes: https://git.openjdk.org/jdk/pull/9399/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9399&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289834
  Stats: 369 lines in 6 files changed: 367 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9399.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9399/head:pull/9399

PR: https://git.openjdk.org/jdk/pull/9399