Import the whole string library, as well as the ctype functions from the musl
C library.  Must is a BSD licensed library that aims to be API and mostly ABI
compatible with glibc, so it's our easiest way to provide the ABI we need
without reinventing the wheel.  I will import more of the traditional non-syscall
C library code from it and expect libc/ to eventually mostly consist of slightly
modified musl code.

Do nothing yet (used for CLOEXEC, meaningless for us).

Various changes to fit into the OSv environment.  This also includes
a ramfs in-memory full filesystem.  Bootfs is rewritten as a simple
unpacker into ramfs, and the fs class is modified to wrap the VFS
instead of being an abstract subclass.

libstdc++ uses this semistandard function in its locale implementation.

The real thing is working already.

This allows generic code to include arch specific code, by eliding the
arch/x64/ prefix.

We will never build a single program containing code from two architectures,
so segregating arch-specific code into a separate namespace is not solving
any problem.  However it makes using arch-specific code from generic code
impossible.

Remove the 86 namespace to fix this.

This implementation stores small objects in pools of similar-sized objects,
while large objects are allocated using a first-fit algorithm.  There is also
a specialized interface for allocating aligned pages.