This feature was added in CMake 3.8. Requiring specific language
features is an outdated approach that CMake stopped supporting in
favor of simply specifyin the specific language standard you want.

https://cmake.org/cmake/help/v3.10/prop_gbl/CMAKE_CXX_KNOWN_FEATURES.html

INTERFACE should be used on dependencies from other than our source files.
PRIVATE should be used the include happens in our source files.

In this case (src/catch2/internal/catch_debug_console.cpp:20) the include
is from our source file.

I encountered a issue with this when building Catch2 for Android in
combination with BUILD_SHARED_LIBS. Changing the visibility to PRIVATE
fixes the issue.

no change in default behavior: -ffile-prefix-map is still added if
supported by compiler but add option for disabling it as it breaks
generic tools for extracting debuginfo/debugsource from build artifacts
like: https://sourceware.org/git/?p=debugedit.git;a=blob;f=scripts/find-debuginfo.in

* Utility for extended mult n x n bits -> 2n bits
* Utility to adapt output from URBG to target (unsigned) integral
  type
* Utility to reorder signed values into unsigned type while keeping
  the order.

Specifically we add
 * `gamma(a, b)`, which returns the magnitude of largest 1-ULP
   step in range [a, b].
 * `count_equidistant_float(a, b, distance)`, which returns the
   number of equi-distant floats in range [a, b].

Co-authored-by: Martin Hořeňovský <martin.horenovsky@gmail.com>

The basic idea was to reduce the number of things dependent on the `Clock`
type. To that end, I replaced `Duration<Clock>` with `IDuration` typedef
for `std::nanoseconds`, and `FloatDuration<Clock>` with `FDuration`
typedef for `Duration<double, std::nano>`. We can generally assume that
any clock's duration can be expressed in nanoseconds, as long as we insert
`duration_cast`s into the right places.

Note that we cannot remove all dependence on `Clock` as a template
arguments, because functions that actually measure the elapsed time have
to use the Clock.

We also changed some template function arguments to pass plain function
pointers, so that the actual implementation can be placed into a cpp file.