Cannot use specialization constants for loop bounds when nonInductiveForLoops = 0

When setting nonInductiveForLoops to 0, specialization constants can not be used as a loop bound as they're not considered constant expressions. As I understand it, for targets not supporting non-inductive loops, these constants would be translated as #defines, and would work, as long as valid values are used that could be assigned to the original constants as well.

Replication glsl:

```
#version 330

precision highp float;

layout (constant_id = 0) const int COUNT = 16;

out vec4 fragOut;

void main()
{
float total = 0.0;
float someOther = 1.0;

for (int i = 0; i < COUNT; i++) {
total += someOther;
}

fragOut = vec4(total);
}
```

Start with the GLSL reproduction in the issue and trace how glslang handles specialization constants used as loop bounds when nonInductiveForLoops is 0. Done means the shown shader accepts a valid specialization-constant loop bound and produces the intended translation for targets without non-inductive loops.

Written by the indexing model from the issue text.