Show deprecation notice in deprecation warnings

If deprecated elements (methods, classes, fields, etc.) are referenced a deprecation warning is created (by default) and the info-box that pops up when one hovers over the element shows generic information:

The deprecation notice (the value of the `@deprecated` tag in the java-doc), which usually contains more details about the replacement and reasoning for the deprecation, is currently only accessible when opening the java-doc of the deprecated element:

It would be convenient if the deprecation notice (the value of the `@deprecated` tag in the java-doc) would also be displayed directly in that info box when one hovers over the deprecation warning in the next paragraph. Usually it contains information about possible replacements.

Since the warning is probably issued by the compiler and shouldn't contain the deprecation notice when building from the CLI, this probably should only be done in jdt.ui.