Update for x86-64 model and tools.

- x64Theory now includes an instruction encoder.
- The functions in x64_stepLib have been renamed, e.g. x64_step is now x64_step_hex.
Give annotations to record field names that appear in updates.

Field names in selections were already annotated.

Closes #191
Tweak output-checking in src/TeX/theory_tests Holmakefile.

Previously, the check would only fail once; on subsequent calls to
Holmake, the test would succeed even though the files had not changed.
The trick is to make the final check a separate and .PHONY target.
bogus README file removed

This file was probably copied from some template, but was never populated
with a meaningful content.
duplicate words removed from .doc files
consistent use of upper-case letters within enumeration
typo: sch(e)matic
consistens use of 'schema' (and not 'scheme') within a single .doc file
typo: a(n) HOL
more duplicate words removed from .doc files
missing dot added
typo: use '\ie' LaTeX macro instead of 'ie'
make non-script files in src/ non-executable
'make clean' should also remove auto-generated 'theorems.tex'

Otherwise 'git status' displays it as 'untracked'.
duplicate words removed from various documentation files

The magic command is:

grep " \([[:alpha:]]\+\) \1[[:space:]]" \
  `find . -name "*.doc" -or -name "*.tex"`

but the output still needs to be filtered by eye, since many duplicates
occur in embedded math and ML.

Duplicates in the Italian manual approved by Domenico Masini.
consistent use of "well-founded(ness)" instead of "wellfounded(ness)"

It was quite unfortunate to mix both forms (i.e. with and without
hyphen) within a single WF_REL_TAC.doc page.