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

Fixes #1236.

Test/baseResults/hlsl.rw.atomics.frag.out

@@ -3945,7 +3945,7 @@ gl_FragCoord origin is upper left
 0:?     'anon@0' (layout( row_major std140) uniform block{ uniform uint u1,  uniform 2-component vector of uint u2,  uniform 3-component vector of uint u3,  uniform uint u1b,  uniform uint u1c,  uniform int i1,  uniform 2-component vector of int i2,  uniform 3-component vector of int i3,  uniform int i1b,  uniform int i1c})
 0:?     '@entryPointOutput.Color' (layout( location=0) out 4-component vector of float)
 
-// Module Version 10200
+// Module Version 10000
 // Generated by (magic number): 80003
 // Id's are bound by 1147