Apache XML Security for C++ 1.4.0 release notes

• Add const specifiers and methods to various classes Committed by SC.
• Add better extraction of openssl build settings using pkg-config Committed by SC.
• Fix exclusive c14n namespace bug (rev. 526939) Committed by BL.
• Fix XSECnew macro to stop catching arbitrary errors and report crypto exceptions instead of turning them into allocation errors Committed by SC.
• Add various missing files to dist target Committed by SC.