unicode-precompose: use fcft's precompose functionality

This allows us more options when determining whether to use a
pre-composed character or not:

We now only use the pre-composed character if it's from the primary
font, or if at least one of the base or combining characters are from
a fallback font.

I.e. use glyphs from the primary font if possible. But, if one or more
of the decomposed glyphs are from a fallback font, use the
pre-composed character anyway.

scripts/generate-unicode-precompose.sh

@@ -1,33 +0,0 @@
-#!/usr/bin/sh
-
-unicodedata_txt="${1}"
-output="${2}"
-
-cat <<EOF > "${output}"
-#pragma once
-
-#include <wchar.h>
-
-static const struct {
-    wchar_t replacement;
-    wchar_t base;
-    wchar_t comb;
-} precompose_table[] = {
-EOF
-
-# extract canonical decomposition data from UnicodeData.txt,
-# - pad hex values to 5 digits,
-# - sort numerically on base character, then combining character,
-# - then reduce to 4 digits again where possible
-#
-# "borrowed" from xterm/unicode/make-precompose.sh
-
-cut "${unicodedata_txt}" -d ";" -f 1,6 |
-    grep ";[0-9,A-F]" | grep " " |
-    sed -e "s/ /, 0x/;s/^/{ 0x/;s/;/, 0x/;s/$/},/" |
-    sed -e "s,0x\(....\)\([^0-9A-Fa-f]\),0x0\1\2,g" |
-    (sort -k 3 || sort +2) |
-    sed -e "s,0x0\(...[0-9A-Fa-f]\),0x\1,g" |
-    sed 's/^/    /' >> "${output}"
-
-echo "};" >> "${output}"