Use CMS object detection from GPA

• src/common.c, src/common.h: Remove old tlv parser code which was the base for the gpa implementation.
• src/mapihelp.cpp, src/mimeparser.c: Use new macro names
• src/parsetlv.c, src/parsetlv.h, src/filetype.c, src/filetype.h: New. Taken from GPA revision 7a5b070
• src/Makefile.am: Add new files

• The filetype code can be used to detect the protocol of decryped content and will be used in decrypt selection.