Allow building from userspace.
Move the defintion of thiszone to print.c.
Make program_name const.
Building libcheri without CHERI-CLANG is no longer supported so remove a
workaround.
Reduce the footprint of locale support.

This forces the C local and fails attempts to change it if
FORCE_C_LOCALE is defined.
Add an option to slim down the timezone code.

When TZ_NO_FILES is defined just fail calls to tzload.
On second thought thiszone belongs in util.c.
Simplify initaliztion for pretty printing.

Conslidate the calls to init_addrtoname and init_checksum into a single
init_print function so tcpdump.c doesn't have to know what is
initialized and init can be differed if desired.
Abstract checking for printers.

tcpdump.c doesn't care what function is used, it just cares if there is a
printer so add a has_printer() function for that purpose.
Reduce the symbol footprint of util.c.

When TCPDUMP_PRINT_ONLY is set, don't implement read_infile() which isn't
used in the printing code.  This file should be split up more sensiably,
but for now this helps.
Add a bunch more functions from libc.
Add David's cmemcpy.
Split the tcpdump Makefile.

The pretty printing stuff moves to Makefile.print to be used by the
upcoming tcpdump-helper.
Initial implementation of tcpdump sandboxing.

The code compiles for me but is completely untested and will need
several stubs to be filled in before it works properly.