D lang compilers have an option -release (or similar) which turns off
asserts, contracts, and other runtime type checking. This patch wires
that up to the b_ndebug flag.
Fixes#7082
Copy the algorithm used by autoconf.
It computes the upper and lower limits by starting at [-1,1] and
multiply by 2 at each iteration. This is even faster for small numbers
(the common case), for example it finds value 0 in just 2 compilations
where old algorithm would check for 1024, 512, ..., 0.
Dylan Baker
Xavier Claessens
Jussi Pakkanen
Haakon Sporsheim
Nirbheek Chauhan