Experimental new redoconf C/C++ build/autoconfiguration system.

To test it out, try this:
	./do -j10 build
	cd docs/cookbook/c
	redo -j10 test

It should detect all the compilers on your system and make three
separate builds for each one: normal, debug, and optimized.  Then it
tries to run a test program under each one.

If there are windows cross compilers and you also have 'wine'
installed, it'll try running the test program under wine as well.

redoconf currently has no documentation other than the example program.
We'll fix that later.

redoconf/utils.sh

@@ -0,0 +1,58 @@
+NL="
+"
+
+# Like 'echo', but never processes backslash escapes.
+# (Some shells' builtin echo do, and some don't, so this
+# is safer.)
+xecho() {
+	printf '%s\n' "$*"
+}
+
+# Returns true if string $1 contains the line $2.
+# Lines are delimited by $NL.
+contains_line() {
+	case "$NL$1$NL" in
+		*"$NL$2$NL"*) return 0 ;;
+		*) return 1 ;;
+	esac
+}
+
+# Split the first (up to) 20 words from $1,
+# returning a string where the words are separated
+# by $NL instead.
+#
+# To allow words including whitespace, you can backslash
+# escape the whitespace (eg. hello\ world).  Backslashes
+# will be removed from the output string.
+#
+# We can use this to read pkg-config output, among other
+# things.
+#
+# TODO: find a POSIX sh way to eliminate the word limit.
+#  I couldn't find an easy way to split on non-backslashed
+#  whitespace without a fork-exec, which is too slow.
+#  If we resorted to bashisms, we could use 'read -a',
+#  but that's not portable.
+rc_splitwords() {
+	xecho "$1" | (
+		read v0 v1 v2 v3 v4 v5 v6 v7 v8 v9 \
+		     v10 v11 v12 v13 v14 v15 v16 v17 v18 v19 \
+		     x
+		if [ -n "$x" ]; then
+			echo "rc_splitwords: too many words" >&2
+			exit 97
+		fi
+		for d in "$v0" "$v1" "$v2" "$v3" "$v4" \
+		         "$v5" "$v6" "$v7" "$v8" "$v9" \
+		         "$v10" "$v11" "$v12" "$v13" "$v14" \
+		         "$v15" "$v16" "$v17" "$v18" "$v19"; do
+			[ -z "$d" ] || xecho "$d"
+		done
+	)
+}
+
+# Escape single-quote characters so they can
+# be included as a sh-style single-quoted string.
+shquote() {
+	printf "'%s'" "$(xecho "$1" | sed -e "s,','\\\\'',g")"
+}