Split header tests accordingly i.e. test core headers as part of
core tests, numeric extension headers as part of numeric tests, etc.
It extends the convention of sub-directories already established in
`include/boost/gil` directory. It is sensible to follow it in other
areas of the source tree (i.e. `test/`, `doc/` and `benchmark/`).
Another important reason to move the tests is to enable removal of
the top-level `Jamfile` with all its definitions of test-specific
requirements.
The top-level `Jamfile` is not advised, especially if it specifies
build requirements like C++ language version.
Those affect non-tests builds e.g. documentation, causing failures
during generation of HTML documentation (leads to missing docs).
Use type traits and features of C++11, then use Boost.MP11.
Remove unused and unnecessary metafunctions in `detail` namespace.
Remove explicit access to ::type as no longer necessary with MP11.
Clean up and reformat code according to the current guidelines.
Legacy tests have been updated where necessary to accommodate
switch to MP11.
Replace std::is_integral with gil::detail::is_channel_integral
Replacing boost::is_integral with std::is_integral is C++ UB:
C++11 / 20.11.2 Header <type_traits> synopsis
1 The behavior of a program that adds specializations for any
of the class templates defined in this subclause is undefined
unless otherwise specified.
Implements also proposal in #93Closes#229
Document maintenance rules of `test/legacy/` content.
Motivation to move the `test/legacy/` is to:
* clarify status of those tests
* make it easier to run tests selectively
* separate new/upcoming feature-specific tests
from those all-in-one tests.
Other changes:
Rename `gil_test_common.hpp` to `unit_test.hpp` to make
it clearer it acts as `boost/test/unit_test.hpp proxy`.
Remove `<include>$(BOOST_ROOT)` from `Jamfile`-s as unnecessary.
