We pass integer uniforms as floating-point ones, which can cause an
exception when converting them to fixed-point values. For example an
integer value of -1 would be 0xFFFFFFFF which is Not-a-Number in
IEEE-754 floating-point and can't be cast to an integer.

In this case we don't actually care about the result because the fixed-
point number is only used by the fixed-function pipeline. A safe but
still fast way to compare floating-point numbers including NaNs is to
treat them as one's complement integers, which can easily be converted
into two's complement representation.

Also rename bitCast<> to bit_cast<> to match the C++20 function.

Change-Id: Id588d25ab70d31eda2800c24a8df539d6a3411d4
Reviewed-on: https://swiftshader-review.googlesource.com/c/21708Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>