doclint should report implicit constructor as missing javadoc comments

If a class has an explicit constructor with no javadoc comments, then running "javadoc -Xdoclint:missing" will produce a warning regarding the missing comments. If, however, no constructor is defined in the source file, which will cause an implicit no-arg constructor to be generated, no warning is generated. Since the implicit constructor will not have any documentation (same as in the explicit case), it would be nice to produce a warning.

To reproduce this, run the attached program as follows:

javadoc -d build --source-path src -Xdoclint:missing pkg