Add -O3 since the libspatialite author uses that optimization level in the build guide for MinGW, and because speed/space savings are important on iOS.
Change libspatialite configure parameters to match the new requirement: libxml2 is enabled by default.
Update libspatialite and its dependencies to the versions detailed on the libspatialite MinGW-w64 build guide (http://www.gaia-gis.it/gaia-sins/mingw64_how_to.html).
Add -O3 since the libspatialite author uses that optimization level in the build guide for MinGW, and because speed/space savings are important on iOS.
Change libspatialite configure parameters to match the new requirement: libxml2 is enabled by default.