Add a strong mode implementation of LUB to fasta; use it to infer ?:

pkg/front_end/test/fasta/kompile.status

Index: pkg/front_end/test/fasta/kompile.status
diff --git a/pkg/front_end/test/fasta/kompile.status b/pkg/front_end/test/fasta/kompile.status
index f4cc172ae78f1673eeabc972f391d444eb680393..ec4f8844599ca6bc8f220a7b7b254b107988d39e 100644
--- a/pkg/front_end/test/fasta/kompile.status
+++ b/pkg/front_end/test/fasta/kompile.status
@@ -57,6 +57,7 @@ unused_methods: Crash
 void-methods: Crash
 
 inference/*: Crash, Fail
+inference/conditional_lub: Pass

[ahe, 2017/05/02 18:32:56]

Ditto.

[Paul Berry, 2017/05/03 17:31:25]

Acknowledged.

 inference/int_upwards_local: Pass
 inference/local_reference_upwards_local: Pass
 inference/type_promotion_simple: Pass