* matrix_info: add information about greatest/smallest value on diagonal
funcitons obsolete - will be replaced
add givens.c, givens.h:
  * implement a very simple matrix datatype
  * function to calculate determinant using givens rotations in order to
    calculate log(det(M))
special function:
  * functions to calculate log of modified bessel functions
obsolete.
The value of log(det(1-M)) will now be calculated using givens rotation
* log_polyintegrate: calculate log of integrals
* use generic function/macro lngamma instead of gsl-function
* bugfix for m==0: A,C,D should be 0, B != 0
see last commit
many, many changes:
* don't use gsl functions, but the functions/macros of sfunc
* use givens rotation to calculate log(det(1-M))
* removed function logdet1m - it is obsolete
* removed other obsolete functions
* set precision
* update Makefile, so that the code compiles
* put flags in separate variables
* add tests for bessel functions
* adjust tests for casimir_Lambda
fixed wrong output file for test
add further tests for casimir_lnLambda