Adds 32 static test vectors for scalar mul, sqr, inv.

These were generated by testing more than 10^12 random test vectors
 for coverage on instrumented (comparison operator outcomes) 32-bit
 and 64-bit code, plus additional edge condition requirements (e.g.
 inputs of 0, 1, -1) and then solving a minimum set cover problem.

The required responses were generated with Sage.

This significantly improves the lcov branch coverage report and
 makes the tests much more sensitive to mutation testing of the
 scalar code.

The challenges and responses are in the form of pairs of scalars:
  C1 * C2 == R1
  (C1 * C2) * (1 / C2) == C1
  C2 * (1 / C2) == 1
  C1 * C1 == R2
  C1^2    == R2