made multithreaded version o seeker.c

http://smp.if.uj.edu.pl/~baryluk/seeker_baryluk.c

i also fixed few problems, and added additionall diagnostics.

compile with:
gcc -o seeker_baryluk -O2 -march=native seeker_baryluk.c -pthread

run:

./seeker_baryluk device number_of_threads

(default 1 thread)