RFR: JDK-8210555: create --source --target synonyms for -source -target

[Jonathan Gibbons]

Please review a mostly-trivial change to add --source and --target as
synonyms for -source and -target in javac and javadoc.

There's also some related test-cleanup.

Here's a brief explanation of the changes, listed in the order given in the
webrev/index.html file.

src/jdk.compiler/share/classes/com/sun/tools/javac/main/Option.java
         Add synonyms in javac

src/jdk.javadoc/share/classes/com/sun/tools/javadoc/main/Start.java
         Replace a hard-coded use of the option name with a symbolic 
reference

src/jdk.javadoc/share/classes/com/sun/tools/javadoc/main/ToolOption.java
         Add synonym in the old/deprecated version of the javadoc tool
         In this version, option aliases are only available using 
distinct ToolOption members

src/jdk.javadoc/share/classes/jdk/javadoc/internal/tool/ToolOption.java
         Add synonym in the main/current version of the javadoc tool
         In this version, option aliases are supported directly, as in javac

test/langtools/jdk/javadoc/tool/api/basic/IsSupportedOptionTest.java
         We don't have good regular testing infrastructure for testing 
javadoc options;
         this test is as good as any for a basic test that the alias is 
recognized.

     test/langtools/jdk/javadoc/tool/sourceOption/SourceOption.java
         There is no code change in this test, but the comment was
         broken, and way too version-specific. The comment is rewritten
         to be less version-specific.

     test/langtools/tools/javac/options/IsSupportedOptionTest.java
         As with the javadoc version of this test given above,
         we don't have good regular testing infrastructure for testing 
javac options;
         this test is as good as any for a basic test that the alias is 
recognized.

     test/langtools/tools/javadoc/sourceOption/SourceOption.java
         This is the version of the SourceOption test for the 
old/deprecated version
         of javadoc. The new comment is a cut-n-paste copy of the new text
         for the version of the test for the standard version of 
javadoc, given above.

test/langtools/tools/javadoc/api/basic/IsSupportedOptionTest.java
         This test was in the set of tests for the old/deprecated 
version of javadoc,
         but was not specific to the old doclet, and the text was almost 
identical
         to the other version, given above. The only differences in the 
text was
         a 1-character difference in the copyright date, and a 
1-character typo
         that has already been corrected in the new version.


JBS: https://bugs.openjdk.java.net/browse/JDK-8210555
Webrev: http://cr.openjdk.java.net/~jjg/8210555/webrev.00/
CSR: https://bugs.openjdk.java.net/browse/JDK-8210556

-- Jon