Revert "Remove remaining occurances of BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION"

This reverts commit 0e563f0db8f1b73a1d8b70c07ea3861a4d2eff5f.
Revert "Require compiler support for partial template specialization."

This reverts commit c26a532032074dc7585d95a8367c9aec6309cfc3.
Revert "Remove obsolete MSVC check from pragma guard"

This reverts commit 54353a7d8924bc58bfc0176339dad0895450790c.
Revert "Config: Remove obsolete MSVC version check"

This reverts commit 9334a55617b2aedb7cc2813e7fd5f721db8f143c.
Add error message when attempting to use a deprecated compiler.
Merge branch 'develop' of https://github.com/boostorg/config into develop
Add check that BOOST_HAS_LONG_LONG is supported on Darwin
before enabling the macro.  Apple helpfully supplies this
macro (__DARWIN_NO_LONG_LONG) if long long type is supported.
This to handle case where compiling with -pedantic causes
compiler errors because it enforces ISO compliance
(c++98 in this case).
Merge pull request #5 from Belcourt/develop

Add check that BOOST_HAS_LONG_LONG is supported on Darwin
Update test for C++11 std::allocator to check that member rebind is a template alias.  Update config headers to match.
Tentative fix for Clang build configuration issue.