Add the actual check to determine, whether n is prime
Add Baillie-PSW header file, fix build
Replace multiplication with the inverse of 2

Whenever we need to divide some k by 2 modulo n, we can either do a
right shift (if k is even) or we can do a right shift on (k+n), since n
is odd.
Try fixing the Frobenius test
Add n%4 to the benchmark programs output
Fix a comment
Split tests into more manageable parts
Rename tests
Fix comment
Add test for mult_x_mod
Add debugging output for failing test
Fix weird power_of_x bug occurring in tests
Nicer comments
A chain addition takes just 4 multiplications

The original assumption of 8 multiplications is for computing more general
products.  Here, we have B_1 = 1, so we can avoid a few multiplications.
In addition, k/2 mod n can be computed by shifting to the right (if k is
even) or shifting (k+n) to the right (if k is odd).