The POSIX standard dictates that during abnormal termination the functions
registered by atexit() are _not_ called, also flushing the streams is
optional. So in this case, it is perfectly legal / better to call the
kernel system call _exit() instead.
This fixes regression issues caused by removal exit() from the kernel.
Squashed commit of the following:
libs/libxx: Fix some confusing in naming. If the directory is called libxx, then the library must be libxx.a (unless perhaps LIBCXX is selected).
libs/: Fix paths in moved library directories.
libs: Brute force move of libc, libnx, and libxx to libs. Cannot yet build it in that configuration.
