Apparently glibc defines it as a macro, so it doesn't compile.  #undef it
back.

Instead of using the variable's value, we used its name.

There isn't even a name for this kind of bug.

Could be better, but waiting for vfs revamp anyway.

Also based on prex code.

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.

Using the recently commited strncmp broke the VFS path lookup.

Unlike most glibc data types, FILE is not opaque - it is defined as _IO_FILE
in libio.h and some glibc inlines actually use it.  So we must use the same
structure.  Do this by subclassing _IO_FILE.

Unbreaks mode=release build.

as in "%016lx".

Convert from libc mutex to osv mutex.

Implemented the wrong prototype.

Just forward the formatted string to debug() for now.  This allows
bringing up a trivial hello world test payload.