This test originally covered both the compiler and library feature-test macros, and was therefore extremely paranoid about checking the behavior of the preprocessor.
We gave the compiler test coverage to the compiler team a long time ago, so we can simplify the library test coverage now.

This commit is a 100% regex search-and-replace, from:

    #ifndef (__cpp_lib_\w+)
    #error \1 is not defined
    #elif \1 != (\d{6}L)
    #error \1 is not \2
    #else
    STATIC_ASSERT\(\1 == \2\);
    #endif

to:

    #ifdef $1
    STATIC_ASSERT($1 == $2);
    #else
    #error $1 is not defined
    #endif

except with \n between each line of the "from" and "to" (presented here on separate lines for clarity).

These are always defined, but to varying values, so they use a slightly different pattern.

This was trying to be extra helpful with a message saying "is OLD_VALUE when it should be NEW_VALUE", but that made the code verbose and unsystematic. This test is passing, so we don't need elaborate error messages in case of failure.

This would never have detected `__cpp_lib_containers_ranges` being defined outside of the relevant mode.

…` again.

This removes all occurrences of "is not defined".

From:

    #else
    #ifdef (__cpp_lib_\w+)
    #error \1 is defined
    #endif
    #endif

to:

    #elif defined($1)
    #error $1 is defined
    #endif

Testing for non-`/clr:pure` mode allows this to follow the consistent pattern.

…r_interconvertible` tests.

These tests weren't doing anything for C++14/17 mode. Now they'll detect the macros being present when they shouldn't be.