Call a writer to dump html; new warning patterns.

* HTML emit functions now take a writer parameter.
  This makes warn_common.py one step closer to the ChromeOS version.
* Add new found warning patterns from java and yacc.

Test: warn.py --url=http://cs/android --separator='?l=' build.log > warnings.html
Test: warn.py --gencsv build.log > warnings.csv
Change-Id: I5c446ca767746598f07603591fdf98f7d82cae17

tools/warn/java_warn_patterns.py

@@ -93,6 +93,8 @@ warn_patterns = [
              [r".*: warning: \[MultipleTopLevelClasses\] .+"]),
     java_low('Avoid having multiple unary operators acting on the same variable in a method call',
              [r".*: warning: \[MultipleUnaryOperatorsInMethodCall\] .+"]),
+    java_low('OnNameExpected naming style',
+             [r".*\.java:.*: warning: .+ \[OnNameExpected\]$"]),
     java_low('Package names should match the directory they are declared in',
              [r".*: warning: \[PackageLocation\] .+"]),
     java_low('Non-standard parameter comment; prefer `/* paramName= */ arg`',