Restore method signatures on MediaType

Previously the method signatures for includes and isCompatibleWith were
incompatible with Spring 3.2.x since the argument was now MimeType.
This caused NoSuchMethodError to be thrown when a class was compiled
against MediaType from Spring 3.2.x and ran against MediaType
from Spring 4.x.

This commit restores the signatures and implements each method by
invoking the super class method.

Issue: SPR-10860