`-g doc-includes` doesn't generate <include> for `-g macro-bindings`

A value-like macro binding ([source](https://github.com/erincatto/box3d/blob/23861418d877fdd97990f35645e845e44a7eb9ec/include/box3d/math_functions.h#L20-L21)):
```c
#define B3_PI 3.14159265359f
```
generates
```cs
[NativeTypeName("#define B3_PI 3.14159265359f")]
public const float B3_PI = 3.14159265359f;
```
without the `` supposedly generated by `-g doc-includes`

Start with include/box3d/math_functions.h lines 20-21 and compare the generated C# for B3_PI when using -g macro-bindings and -g doc-includes. Confirm that the value-like macro's [NativeTypeName] output is missing an and verify the corrected generated output.

Written by the indexing model from the issue text.