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/rc/pkg-config.rc.od

@@ -0,0 +1,17 @@
+. ./redoconf.rc
+rc_include
+
+for d in "$PKG_CONFIG" pkg-config; do
+	rc_undo
+	if "$d" --version >/dev/null 2>&1; then
+		rc_replaceln PKG_CONFIG "$d"
+		rc_replaceln HAVE_PKG_CONFIG 1
+		rc_save
+		exit 0
+	fi
+done
+
+# Failed
+rc_replaceln HAVE_PKG_CONFIG ""
+rc_replaceln PKG_CONFIG ""
+rc_save