Implement new potential directive keyword test

Now we can use directive names as variables and targets type, for
example:

print = foo # variable
print{foo}: # target

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/keyword/buildfile b/tests/keyword/buildfile
new file mode 100644
index 0000000..cd91d33
--- /dev/null
+++ b/tests/keyword/buildfile
@@ -0,0 +1,23 @@
+# Quoting.
+#
+"print"  = a
+'print' += b
+pr"int" += c
+print'' += d
+
+# Not = or +=.
+#
+print += e
+
+print $print
+
+# <name>(
+#
+print(test)
+
+# Separated.
+#
+define print: file
+print{foo}:
+
+./: