built year level index.html files

Added `bin/all-years.sh` to run a command over all years.

Added `bin/gen-year-index.sh` to build an `index.html`
for a given year.

Added support code to build an `index.html`
for a given year.

Added `make gen_year_index` to to level Makefile
and related rules.

Using the above, added `index.html` files for all IOCCC years.

Updated `bin/README.md` according to the above.

Improved comments in `bin/all-run.sh`.

Exported TOPDIR in all `bin/` tools that use TOPDIR.

Removed incorrect lines in `bin/quick-readme2index.sh`
usage message.

Improve -v 3 printed important variables messages,
in order that important variables are exported,
from all `bin/` tools.

Rebuild all HTML pages via `make www`.

bin/sort.gitignore.sh

@@ -79,6 +79,7 @@ status="$?"
 if [[ $status -eq 0 ]]; then
     TOPDIR=$("$GIT_TOOL" rev-parse --show-toplevel)
 fi
+export TOPDIR
 export REPO_URL="https://github.com/ioccc-src/temp-test-ioccc"
 export TOP_URL="https://ioccc-src.github.io/temp-test-ioccc"
 export SGI_TOOL="bin/sgi.sh"
@@ -309,13 +310,16 @@ fi
 # parameter debugging
 #
 if [[ $V_FLAG -ge 3 ]]; then
+    echo "$0: debug[3]: VERSION=$VERSION" 1>&2
     echo "$0: debug[3]: NAME=$NAME" 1>&2
-    echo "$0: debug[3]: YEAR_DIR=$YEAR_DIR" 1>&2
+    echo "$0: debug[3]: V_FLAG=$V_FLAG" 1>&2
+    echo "$0: debug[3]: GIT_TOOL=$GIT_TOOL" 1>&2
+    echo "$0: debug[3]: TOPDIR=$TOPDIR" 1>&2
     echo "$0: debug[3]: REPO_URL=$REPO_URL" 1>&2
     echo "$0: debug[3]: TOP_URL=$TOP_URL" 1>&2
     echo "$0: debug[3]: SGI_TOOL=$SGI_TOOL" 1>&2
-    echo "$0: debug[3]: DO_NOT_PROCESS=$DO_NOT_PROCESS" 1>&2
     echo "$0: debug[3]: NOOP=$NOOP" 1>&2
+    echo "$0: debug[3]: DO_NOT_PROCESS=$DO_NOT_PROCESS" 1>&2
     echo "$0: debug[3]: ENTRY_PATH=$ENTRY_PATH" 1>&2
     echo "$0: debug[3]: REPO_NAME=$REPO_NAME" 1>&2
     echo "$0: debug[3]: BIN_PATH=$BIN_PATH" 1>&2