SPV Version: Emit the requested SPIR-V version, not the header version.

Fixes #1236.
diff --git a/Test/baseResults/spv.400.frag.out b/Test/baseResults/spv.400.frag.out
index e1d3da9..3f73f5b 100644
--- a/Test/baseResults/spv.400.frag.out
+++ b/Test/baseResults/spv.400.frag.out
@@ -1,5 +1,5 @@
 spv.400.frag
-// Module Version 10200
+// Module Version 10000
 // Generated by (magic number): 80003
 // Id's are bound by 1118