Mac build instruction updates

Some small tweaks to the mac build instructions to reflect what worked on my system:
(OSX 10.10 and OS X 10.6, with 10.6 SDK, wxWidgets 2.9.5)

- Update "osx_gl_hw_accel.patch" to have the full path to the glcanvas.mm to patch, because there are multiple files with that name
- Delete "Drag and Drop.diff" as it is already applied in wxWidgets 2.9.5.
- Mac/Build.txt: specify `--without-liblzma` to wxWidgets configure to avoid an error while building wxWidgets 2.9.5: " ../src/tiff/libtiff/tif_lzma.c:39:10: fatal error: 'lzma.h' file not found". I got this same error on two systems (one 10.10 and one 10.6) so it seems to be an issue with wx 2.9.5, also it seems others have had similar issues: http://comments.gmane.org/gmane.comp.lib.wxwidgets.devel/149306