Extremely basic integration of wvtest for testing.

And move test scripts into t/ subdir to keep things clean.

As part of that, make sure redo adds itself to the PATH on startup so that
subscripts can find it.

t/CC.do

@@ -0,0 +1,4 @@
+cat <<-EOF
+	gcc -Wall -o /dev/fd/1 -c "\$1"
+EOF
+chmod a+x $3

t/LD.do

@@ -0,0 +1,6 @@
+cat <<-EOF
+	OUT="\$1"
+	shift
+	gcc -Wall -o "\$OUT" "\$@"
+EOF
+chmod a+x $3

t/hello.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main()
+{
+    printf("hello, world!\n");
+    return 0;
+}

t/hello.do

@@ -0,0 +1,2 @@
+redo --ifchange LD hello.o
+./LD hello hello.o

t/hello.o.do

@@ -0,0 +1,2 @@
+redo --ifchange CC hello.c
+./CC hello.c

t/it.do

@@ -0,0 +1 @@
+redo --ifchange hello

t/runtests.do

@@ -0,0 +1,2 @@
+redo --ifchange it
+./hello >&2