Dead code in FastMath.pow(double, double) and some improvement in test coverage

This issue concerns the FastMath class and its test class.

(1) In the double pow(double, double) function, there are 2 identical "if" blocks. The second one can be suppressed.
if (y < 0 && y == yi && (yi & 1) == 1)

{ return Double.NEGATIVE_INFINITY; }

// this block is never used -> to be suppressed
if (y < 0 && y == yi && (yi & 1) == 1)

{ return -0.0; }

if (y > 0 && y == yi && (yi & 1) == 1) { return -0.0; }

(2) To obtain better code coverage, we added some tests case in FastMathTest.java (see attached file)

• Added test for log1p
• Added tests in testPowSpecialCases()
• Added tests for a 100% coverage of acos().
• Added tests for a 100% coverage of asin().