This will make things as std::to_string() and other C++ features
work with a modern and supported C++ library.
We package up libc++_shared.so and bump the revision of every C++
using package to make it rebuild against it.
Users who have built C++ using libraries or programs will probably
need to rebuild them if they are linked against Termux-supplied
libraries, as user code was previously linked against gnustl while
the system libraries are now using libc++, and it's not a good idea
to mix C++ standard libraries in a program.
32-bit android uses 32-bit off_t by default. When building with
-D_FILE_OFFSET_BITS=64 with unified headers off_t are promoted
to 64-bit, but there are bugs in the toolchain and spotty support
for it in the platform (not all functions are available until
android-24, and the platform zlib is compiled with 32-bit off_t).
Also, unless every library&program is rebuilt with 64-bit off_t,
including user-built ones, we risk a mismatch between programs and
libraries which can cause serious (but sometimes subtle) runtime
failures.
As -D_FILE_OFFSET_BITS=64 is not that important for most users
(with mariadb requiring it as an exception), we drop the support
for now by patching it away in <sys/cdefs.h>.
