Add an Expect-like tool

This is to provide an Expect utility with a minimal dependency tree
for C-based projects.  It also addresses some Tcl Expect design issues,
as perceived by me.

tools/wdye/test.lua

@@ -0,0 +1,24 @@
+for k, v in pairs(wdye) do _G[k] = v end
+
+-- The terminal echoes back, we don't want to read the same stuff twice.
+local cat = spawn {"sh", "-c", "cat > /dev/null", environ={TERM="xterm"}}
+assert(cat, "failed to spawn process")
+assert(cat.term.key_left, "bad terminfo")
+
+cat:send("Hello\r")
+local m = expect(cat:exact {"Hello\r", function (p) return p[0] end})
+assert(m == "Hello\r", "exact match failed, or value expansion mismatch")
+
+local t = table.pack(expect(timeout {.5, 42}))
+assert(#t == 1 and t[1] == 42, "timeout match failed, or value mismatch")
+
+cat:send("abc123\r")
+expect(cat:regex {"A(.*)3", nocase=true, function (p)
+	assert(p[0] == "abc123", "wrong regex group #0")
+	assert(p[1] == "bc12", "wrong regex group #1")
+end})
+
+-- Send EOF (^D), test method chaining.
+cat:send("Closing...\r"):send("\004")
+local v = expect(cat:eof {true},
+	cat:default {.5, function (p) error "expected EOF, got a timeout" end})