Add stub or stdout only versions of a number of stdio and output related
functions.
Add a malloc based on the one from rtld-elf.

This includes a full implementation of calloc, free, malloc, realloc,
and reallocf.
The owner of /usr/share/images should be root.
Remove cheritest-helper's stub malloc.
Return to building tcpdump as normal.

It's not necessicary to build specially since we're sandboxing a
cheri_tcpdump.  It is also failing to link for me when built through the
bsdtools build system.
Remove a bunch of stubs made redundant by additions to libc_cheri.
Add a test for malloc and free in a sandbox.