mariadb: fix clang and darwin build

The contents of `clang-isfinite.patch` are no longer necessary after
upstream revision 031fa6d4258574379ca3c1cbe912d235e9581982, which
includes a similar change.

Building in c++11 mode removes support for the GCC `typeof` extension
in favor of the standardized `__typeof__`. This causes errors when
using the `strmake_buf` macro, which relies on `typeof`.