Revive config_test.c

Move config-dependent code (recvwithttl) from net.c to mdp_net.c (new)

Move log-implementation-independent code from log.c to log_util.c (new)

Build config_test binary in Makefile
Deprecate RHIZOME_MANIFEST_ID_... in favour of RHIZOME_BUNDLE_ID_...
Consolidate Rhizome string parsing functions

Remove unused rhizome_str[n]_is_...() functions in favour of
str[n]_to_rhizome_..._t() functions

Ensure that all str_to_..._t() functions accept a NULL 'dst' pointer
so they can be used easily to validate strings
Add missing copyright/license comment blocks

Update a few existing copyright notices to reflect recent work
Enforce valid Rhizome 'service' and 'name' strings
Improve test framework: forked commands inherit stdin

Remove the subshell parentheses around the command invoked using fork(),
so that the forked command inherits the file descriptors.  This allows
it to be used like "fork some command < input".
Improve test framework: include %label in fork log
Merge branch 'development' into 'naf4'

Remove two redundant calls to rhizome_retrieve_manifest() in meshms.c,
revealed by an assert() in the stricter manifest parsing code

Fix header files included by socket.h
Merge branch 'install-target' of github.com:petterreinholdtsen/serval-dna into install-target
Fix 'make install' target, add 'make uninstall'

Define $(sbindir) and $(exec_prefix)

Define $(INSTALL), $(INSTALL_PROGRAM) and $(INSTALL_DATA)

Use $(RM) instead of rm -f
Add CONTRIBUTORS.md file, fix alternative links in README.md
Remove alternative links from README.md

GitHub have fixed the README Markdown rendering on the
repository home page, so alternative links are no longer
needed
Merge branch 'naf4' into 'development'

Copyright notices added to most source files and headers

New 'config_test' make target

Add RHIZOME_BUNDLE_ID_xxx, deprecate RHIZOME_MANIFEST_ID_xxx

Consolidate Rhizome string functions
Add full text of GPL version 2.0
Uniform copyright notices

Added some missing copyright/license block comments
Uniform #ifdef __SERVAL_DNA__... for headers
Add "servald version" command and "make copyright"

New COPYRIGHT.txt is regenerated manually using "make copyright" which
invokes the sp-copyright-tool utility from the serval-tools repo.
Update README

Licensing and copyright, MeshMS, Rhizome
Fix formatting issues
Add link arguments so the linker can find math functions