getline: split out for darwin systems

At least on OS X 10.5 and older, getline does not exist.  So split out the
function from the mingw code so that we can pull it in for Darwin systems.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/tools/getline.h b/tools/getline.h
new file mode 100644
index 0000000..a2f35b9
--- /dev/null
+++ b/tools/getline.h
@@ -0,0 +1 @@
+int getline(char **lineptr, size_t *n, FILE *stream);