Math: minor test cleanup.
Math: added minmax() and Vector2::minmax().

No Vector<size, T> and std::initializer_list versions yet, as the
algorithm for it is pretty complicated and I'm not sure that they will
be used frequently enough to deserve their existence.
Doc++
Fixed ColorTest on ES.
Ensure that all GL tests have `*GLTest` suffix.

Makes it easier to selectively run GL/non-GL tests.
Fixed BufferGLTest on ES2 non-deprecated build.

Combinatorial explosion of build problems.
MagnumFont: fixed compilation with Clang.
TgaImporter: fix test on ES2.
Fixed constexpr issues in ColorTest under GCC 4.6.
TgaImporter: ColorFormat::Luminance is available only on ES2.
Trade: explicitly link tests to CORRADE_PLUGINMANAGER_LIBRARIES.

Compilation of tests in static build fails with missing
reference to dlclose().
Audio: missing inline.

Caused static build to fail on multiple definitons.
Link CORRADE_PLUGINMANAGER_LIBRARIES to all plugin-enabled executables.

Should fix another bunch of static build errors.
Hopefully finally fixed constexpr issues in ColorTest with GCC 4.6.

Follow-up to 80b61be4851910d575547516e6ce75b883aca4a4, I am too lazy to
test it before commiting.
Properly fix linking to libdl.

Use CORRADE_PLUGINMANAGER_LIBRARIES instead of
CORRADE_PLUGINMANAGER_LIBRARY when linking core Magnum library.

This reverts commit 80263eb318034e1617e5cf7faddff63f411a0b82 and
6dbe31f0f03856d78b61d7214a3ded49f70010cf.
Rename also classes and files for GL tests.
Use plural form also for CORRADE_UTILITY_LIBRARIES.
package: Jenkins CI configuration.
Moved development PKGBUILDs to `package/archlinux`.

They cluttered the root project dir way too much.
package: added Clang PKGBUILD.