COMP: Define ITKCommon_EXPORT_EXPLICIT for Doxygen.

For:

  ITK/Modules/Core/Common/include/itkMetaDataObject.h:215: warning: documented
  symbol `template class ITKCommon_EXPORT_EXPLICIT itk::MetaDataObject<
  std::string >' was not declared or defined.

Change-Id: Idbf8f991788d681f7cda18abaee4f9241c274e7a
COMP: StdStreamStateSave Doxygen include.

Fix warning:

  ITK/Modules/Core/Common/include/itkStdStreamStateSave.h:33: warning:
  explicit link request to 'include' could not be resolved

Change-Id: I6e90a3870e0380f37afdd9e3e16b692966385414
Merge topic 'doxygen-warnings'

acc1817a COMP: StdStreamStateSave Doxygen include.
1ddedcd6 COMP: Define ITKCommon_EXPORT_EXPLICIT for Doxygen.