math/single contained code for systems without double precision fpu
and rem_pio2 is not used currently and likely will be designed
differently when double precision trigonometric functions are added.

Scripts are known to work with sollya 6.0.

Add a single makefile such that it will rarely need modifications
with regular source code changes.

The usual configure step for build environment detection is done
manually by editing config.mk, it is expected to be simple make
variable changes (mostly CFLAGS), later a simple configure script
can be added to generate config.mk if necessary.

Update the README.