Use the correct type for the constant for matrix/scalar division

When a matrix is divided by a scalar it tries to take the reciprocal
of the scalar to convert the operation into a multiply. However it was
always doing this by making a 32-bit constant. If the scalar is a
double then this would end up making an FDiv instruction with
different types in the operands.

This patch adds a helper method called makeFpConstant which makes a
floating-point constant of the given type. The code to take the
reciprocal now uses it to make the same type as the result.

Fixes https://github.com/KhronosGroup/glslang/issues/1278

SPIRV/GlslangToSpv.cpp

@@ -4137,7 +4137,8 @@ spv::Id TGlslangToSpvTraverser::createBinaryMatrixOperation(spv::Op op, spv::Dec
     case spv::OpFDiv:
         if (builder.isMatrix(left) && builder.isScalar(right)) {
             // turn matrix / scalar into a multiply...
-            right = builder.createBinOp(spv::OpFDiv, builder.getTypeId(right), builder.makeFloatConstant(1.0F), right);
+            spv::Id resultType = builder.getTypeId(right);
+            right = builder.createBinOp(spv::OpFDiv, resultType, builder.makeFpConstant(resultType, 1.0), right);
             op = spv::OpMatrixTimesScalar;
         } else
             firstClass = false;