Fix uniform_real_distribution_fp16 warning and single Dimension increment

- Change uniform_real_distribution_fp16's arguments to float to avoid maybe-uninitialized warnings in half data type's copy constructor and converter
- Add increment method to Dimensions in order to avoid possible overflows when incrementing single dimensions
- Remove internal_only flag documentation

Resolves: COMPMID-4061

Change-Id: I7c50487193bd7b47b03d52fc595840c7df4e7104
Signed-off-by: Giorgio Arena <giorgio.arena@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/4760
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/tests/validation/reference/ColorConvertHelper.h b/tests/validation/reference/ColorConvertHelper.h
index 100b4dc..0656b36 100644
--- a/tests/validation/reference/ColorConvertHelper.h
+++ b/tests/validation/reference/ColorConvertHelper.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2019 Arm Limited.
+ * Copyright (c) 2017-2021 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -614,9 +614,7 @@
 
     rgb_to_yuv_calculation(rvec, gvec, bvec, dst[0], uvec_top, uvec_bottom, vvec_top, vvec_bottom);
 
-    int         uvec_coord_x = 0;
-    int         uvec_coord_y = 0;
-    Coordinates uvec_coord{ uvec_coord_x, uvec_coord_y };
+    Coordinates uvec_coord{};
     for(int y = 0; y < height; y++)
     {
         for(int x = 0; x < width; x += 2)
@@ -638,7 +636,7 @@
             plane_2_pixel[0] = vvec_top_val;
             plane_2_pixel[1] = vvec_bottom_val;
 
-            uvec_coord.set(0, ++uvec_coord_x);
+            uvec_coord.increment(0);
         }
     }
 }