+ attempt to get compile working for other compiler's and systems including another attempt to sort out bit manipulation intrinsics in arith.h. seems to work now for MSVC/x64, msys2/mingw64, and linux/gcc.
+ translated some QS tdiv routines to intrinsics for MSVC builds
+ added sigma() and totient() functions to calc.c
+ fixed bug where a command line of just an input number causes memory corruption (thanks Ferrier!)