Cleanup: move public doc-strings into headers for 'gpu'

Ref T92709

source/blender/gpu/GPU_batch_utils.h

@@ -30,6 +30,16 @@ extern "C" {
 struct rctf;
 
 /* gpu_batch_utils.c */
+
+/**
+ * Creates triangles from a byte-array of polygons.
+ *
+ * See 'make_shape_2d_from_blend.py' utility to create data to pass to this function.
+ *
+ * \param polys_flat: Pairs of X, Y coordinates (repeating to signify closing the polygon).
+ * \param polys_flat_len: Length of the array (must be an even number).
+ * \param rect: Optional region to map the byte 0..255 coords to. When not set use -1..1.
+ */
 struct GPUBatch *GPU_batch_tris_from_poly_2d_encoded(
     const uchar *polys_flat, uint polys_flat_len, const struct rctf *rect) ATTR_WARN_UNUSED_RESULT
     ATTR_NONNULL(1);
@@ -37,7 +47,11 @@ struct GPUBatch *GPU_batch_wire_from_poly_2d_encoded(
     const uchar *polys_flat, uint polys_flat_len, const struct rctf *rect) ATTR_WARN_UNUSED_RESULT
     ATTR_NONNULL(1);
 
-/* Only use by draw manager. Use the presets function instead for interface. */
+/**
+ * Replacement for #gluSphere.
+ *
+ * \note Only use by draw manager. Use the presets function instead for interface.
+ */
 struct GPUBatch *gpu_batch_sphere(int lat_res, int lon_res) ATTR_WARN_UNUSED_RESULT;
 
 #ifdef __cplusplus