8066843: Messager.printMessage cannot print multiple errors for same source position
Summary: Using a DiagnosticFlag to mark diagnostics that should be always printed even if multiple of them have the same source position.
Reviewed-by: darcy, jjg, mcimadamore
Test.java:14: error: anchor already defined: "dupTest"
* <a name="dupTest">dupTest again</a>
^
Test.java:24: error: anchor already defined: "dupTestField"
/** <a name="dupTestField">dupTestField again</a> */
^
Test.java:27: error: anchor already defined: "dupTestMethod"
/** <a name="dupTestMethod">dupTestMethod again</a> */
^
Test.java:32: error: anchor already defined: "dupNested"
* <a name="dupNested">dupNested again</a>
^
Test.java:40: error: anchor already defined: "dupNestedField"
* <a name="dupNestedField">dupNestedField</a>
^
Test.java:47: error: anchor already defined: "dupNestedMethod"
* <a name="dupNestedMethod">dupNestedMethod</a>
^
6 errors