* src/EmbeddedFiles.h|cpp: add validate() function to validate loaded .lyx file.
* src/LayoutFile.h|cpp: add Layout_Type parameter to addLayoutFile to load an embedded layout.
* src/BufferParams.h|cpp: read layout from temp directory, then local directory.
* src/frontends/qt4/GuiDocument.cpp: handle embedded layout type
* src/LyXFunc.cpp: handle embedded layout when a layout is re-read.
* src/Buffer.cpp: validate after a buffer is read. handle exceptions properly.
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@23667 a592a061-630c-0410-9148-cb99ea01b6c8