8184969: Cannot specify multiple -link to jdk9 javadoc
Reviewed-by: jjg

8177848: Rename Configuration(Impl) classes
Reviewed-by: jjg

8164130: Simplify doclet IOException handling
Reviewed-by: bpatel, ksrini

8149903: Fix other Extern.
Reviewed-by: darcy

8035473: [javadoc] Revamp the existing Doclet APIs
8146529: Update the new Doclet API
8146427: "-nohelp" option issue
8146475: "-helpfile" option issue
Reviewed-by: alanb, bpatel, ihse, jjg, jlahoda, mchung, ogb, vromero