Merge pull request #518 from melissalinkert/rebased/develop/e283fb8e38042f5b0da2578e7c7fb07f838b92ca

ScanR: clear the pixel buffer when an invalid TIFF is found (rebased onto develop)
Merge pull request #519 from melissalinkert/cxd-dimensions-develop

.cxd dimension detection fixes (rebased onto develop)
merge develop -D org -I include -E exclude: PR 512 (xsd-fu: Extend C++ support to generate headers and include guards)
merge develop -D org -I include -E exclude: PR 521 (Assorted bug fixes for May)