Add parameter category qualifier "forward" (current qualifiers are "in", "out", and "in_out") based on http://www.modernescpp.com/index.php/c-core-guidelines-how-to-pass-function-parameters. Add new usage syntax BOOST_PARAMETER_NAME((object-name), namespace-name) qualifier(tag-name)) and BOOST_PARAMETER_NAME(qualifier(name)). (Existing code that uses qualifiers directly and correctly with BOOST_PARAMETER_FUNCTION and other code generation macros should remain unaffected for now, so no breaking changes.) The reason for the change in usage is to enable applying of parameter category constraints to Boost.Parameter-enabled functions and constructors invoked through argument composition. (Otherwise, it is currently possible to use argument composition to bypass parameter category constraints applied in BOOST_PARAMETER_FUNCTION et. al.) See "test/compose.cpp" for example usage.
test/compose.cpp:
Change workarounds from boost::function to std::function since msvc-11.0 reports having a C++11-compliant <functional> header.
Add LIBS_PARAMETER_TEST_RUN_FAILURE configuration macro to facilitate run-fail testing.
test/Jamfile.v2:
Replaced deprecated test-suite statement with alias statements.
Added run-fail test case under its own alias statement.
appveyor.yml:
Add mingw compiler configurations to the test matrix.
Update msvc-11.0 configuration to also execute the run-fail test.
travis.yml:
Ensure that only the standard tests are run, not the run-fail test.
