Add an integration test for %include.

src/test/conf_examples/include_1/expected

@@ -0,0 +1,3 @@
+ContactInfo includefile@example.com
+Nickname nested
+ORPort 8008

src/test/conf_examples/include_1/included.inc

@@ -0,0 +1,4 @@
+
+ContactInfo includefile@example.com
+
+%include "nested.inc"

src/test/conf_examples/include_1/nested.inc

@@ -0,0 +1,2 @@
+
+Nickname nested

src/test/conf_examples/include_1/torrc

@@ -0,0 +1,4 @@
+
+%include "included.inc"
+
+ORPort 8008