* PKGBUILD:
- add the template Makefile.ext.in governing the compilation and installation
of all relevant sqlite extensions
- reactivate the split-package function 'package_sqlite-extensions'
- remove all the obsolete code used by the patch removed in the previous commit
* Makefile.ext.in:
- add the Makfefile template for building and installing sqlite extensions directly
from source code.
* README.md.in:
- add README file about loading sqlite extensions
