For projection mapping systems, sometimes large textures are needed but it's impossible to create it because RenderTexture size is limited to 16K.

To reproduce:

1. Download attached project "TextureSizeLimit.zip" and open in Unity
2. On Project window, right click, select "Create/RenderTexture (16K x 16)" and left click created RenderTexture
Note: Observe that everything is fine and no error is given in Console
3. On Project window, right click, select "Create/RenderTexture (16K+1 x 16)" and left click created RenderTexture
Note: Observe that in Console you will get two same errors:

RenderTexture.Create failed: requested size is too large.
UnityEditor.DockArea:OnGUI()

Notes:
- This issue appears on both Windows and OSX

Reproduced on Unity 2017.1.3p1, 2017.2.1p3, 2017.3.0p4, 2018.1.0b5 and 2018.2.0a1