Lecture 3, self-exercise 1 solution: ex1.c

Anton Goncharenko reported the following problem of the previous version:

109: main: Assertion `FloatEqualEpsilon(RectangleArea(good_rect), 0.81)' failed.

To fix it, this version implements a new FloatEqualEpsilon() that converts floats to integers for comparison. See Comparing Floating Point Numbers, 2012 Edition and AlmostEquals() from Google Test.