Fix #1395: GLSL volatile maps to SPIR-V Volatile and Coherent.

The major version number was bumped in the previous commit to support
this.
diff --git a/SPIRV/GlslangToSpv.cpp b/SPIRV/GlslangToSpv.cpp
index 749d013..6d89109 100755
--- a/SPIRV/GlslangToSpv.cpp
+++ b/SPIRV/GlslangToSpv.cpp
@@ -340,8 +340,10 @@
 {
     if (qualifier.coherent)
         memory.push_back(spv::DecorationCoherent);
-    if (qualifier.volatil)
+    if (qualifier.volatil) {
         memory.push_back(spv::DecorationVolatile);
+        memory.push_back(spv::DecorationCoherent);
+    }
     if (qualifier.restrict)
         memory.push_back(spv::DecorationRestrict);
     if (qualifier.readonly)