added some #defines to change compile options for printf statements
added -f options to rm's in make clean so that clean doesn't error out
created Makefile for p37
added sum to end of problem 37
completed p27
changed final printf to include multiple of a and b, increased efficiency of prime sieve
fixed sieve in p37
added Makefile for p27
changed executable name
changed executable name of Makefile for p23
removed excessive debug printing