Bump Assimp version number to 4.1.0.

Close #2268.

Docs/Urho3D.dox

@@ -231,7 +231,7 @@ Urho3D uses the following third-party libraries:
 - MojoShader (https://icculus.org/mojoshader)
 - Mustache 1.0 (https://mustache.github.io, https://github.com/kainjow/Mustache)
 - nanodbc 2.12.4+ (https://lexicalunit.github.io/nanodbc)
-- Open Asset Import Library 4.0.1 (http://assimp.sourceforge.net)
+- Open Asset Import Library 4.1.0 (http://assimp.sourceforge.net)
 - pugixml 1.7 (http://pugixml.org)
 - rapidjson 1.1.0 (https://github.com/miloyip/rapidjson)
 - Recast/Detour (https://github.com/memononen/recastnavigation)

README.md

@@ -194,7 +194,7 @@ Urho3D uses the following third-party libraries:
 - MojoShader (https://icculus.org/mojoshader)
 - Mustache 1.0 (https://mustache.github.io, https://github.com/kainjow/Mustache)
 - nanodbc 2.12.4+ (https://lexicalunit.github.io/nanodbc)
-- Open Asset Import Library 4.0.1 (http://assimp.sourceforge.net)
+- Open Asset Import Library 4.1.0 (http://assimp.sourceforge.net)
 - pugixml 1.7 (http://pugixml.org)
 - rapidjson 1.1.0 (https://github.com/miloyip/rapidjson)
 - Recast/Detour (https://github.com/memononen/recastnavigation)