loci: move special offset/length macros to loci_int.h
loci: move IS_FLOW_MOD_SUBTYPE macro to loci_int.h
loci: split accessors into one file per class
loci: rename gen_all_accessor_definitions to gen_list_accessor_definitions
loci: generate list accessors in their own files
loci: move init/new function definitions to the class's file
loci: generate header classes
loci: output pragmas to each class C file
loci: move setup_from_add functions to a new C file
loci: move string tables to their own file
loci: move init function map to its own file

Dropped the header class special case, seems to work without it.
loci: stop generating empty loci.c
loci: build a static loci library in locitest

Having the static library target is useful for benchmarking the build.
Makefile: add parallelism to the locitest build
loci: trim includes
loci: move push_wire_types functions to their class's C file
loci: move per-class declarations to loci_classes.h

The goal is to free loci.h of dynamically generated code and turn it into a
static template.

Needed to move some declarations out of loci.h and into of_object.h, where they
really belonged anyway.
loci: move of_object_parent_length_update to of_object.c

This function did not need to be inlined.
loci: remove dead gen_fn_ptrs/gen_unified_fns options

Only support unified accessors.
loci: remove config_check and code_gen_config

There's nothing to configure.