Directory reorg: move code into redo/, generate binaries in bin/.

It's time to start preparing for a version of redo that doesn't work
unless we build it first (because it will rely on C modules, and
eventually be rewritten in C altogether).

To get rolling, remove the old-style symlinks to the main programs, and
rename those programs from redo-*.py to redo/cmd_*.py.  We'll also move
all library functions into the redo/ dir, which is a more python-style
naming convention.

Previously, install.do was generating wrappers for installing in
/usr/bin, which extend sys.path and then import+run the right file.
This made "installed" redo work quite differently from running redo
inside its source tree.  Instead, let's always generate the wrappers in
bin/, and not make anything executable except those wrappers.

Since we're generating wrappers anyway, let's actually auto-detect the
right version of python for the running system; distros can't seem to
agree on what to call their python2 binaries (sigh). We'll fill in the
right #! shebang lines.  Since we're doing that, we can stop using
/usr/bin/env, which will a) make things slightly faster, and b) let us
use "python -S", which tells python not to load a bunch of extra crap
we're not using, thus improving startup times.

Annoyingly, we now have to build redo using minimal/do, then run the
tests using bin/redo.  To make this less annoying, we add a toplevel
./do script that knows the right steps, and a Makefile (whee!) for
people who are used to typing 'make' and 'make test' and 'make clean'.

version/vars.do

@@ -1,40 +0,0 @@
-redo-ifchange gitvars prodname
-
-read PROD <prodname
-
-exec <gitvars
-read COMMIT
-read NAMES
-read DATE
-
-# the list of names is of the form:
-#   (x,y,tag: $PROD-####,tag: $PROD-####,a,b)
-# The entries we want are the ones starting with "tag: $PROD-" since those
-# refer to the right actual git tags.
-names_to_tag()
-{
-	x=${1#\(}
-	x=${x%\)}
-	cur=
-	while [ "$cur" != "$x" ]; do
-		x=${x# }
-		x=${x#tag: }
-		cur=${x%%,*}
-		tagpost=${cur#$PROD-}
-		if [ "$cur" != "$tagpost" ]; then
-			echo "$tagpost"
-			return 0
-		fi
-		x=${x#*,}
-	done
-	commitpost=${COMMIT#???????}
-	commitpre=${COMMIT%$commitpost}
-	echo "unknown-$commitpre"
-}
-
-
-sTAG=$(names_to_tag "$NAMES")
-
-echo "COMMIT='$COMMIT'"
-echo "TAG='$sTAG'"
-echo "DATE='${DATE%% *}'"