websocketpp: add various upstream accepted and proposed patches to fix various issues, including:

- build failure with boost 1.71
- bad installation of header files correct version on some OSes.
- fix version minor number
- fix Scons script not being Python3 ready
- build examples and tests only if ptest is enabled in DISTRO_FEATURES
- do not depend on websocketpp from -dev package, because this is an header only dev package for now

Signed-off-by: Gianfranco Costamagna <costamagnagianfranco@yahoo.it>
Signed-off-by: Gianfranco Costamagna <locutusofborg@debian.org>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
(cherry picked from commit 7cd2604172)
Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-oe/recipes-support/websocketpp/websocketpp-0.8.1/771.patch

@@ -0,0 +1,22 @@
+From 4bccfb04a264704ec9b80ba332ee1cf113ce7f1b Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Wolfgang=20St=C3=B6ggl?= <c72578@yahoo.de>
+Date: Thu, 1 Nov 2018 20:58:10 +0100
+Subject: [PATCH] Update version number in CMakeLists.txt to 0.8.1
+
+---
+ CMakeLists.txt | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 2786aba9..2d13117b 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -24,7 +24,7 @@ endif ()
+ ############ Project name and version
+ set (WEBSOCKETPP_MAJOR_VERSION 0)
+ set (WEBSOCKETPP_MINOR_VERSION 8)
+-set (WEBSOCKETPP_PATCH_VERSION 0)
++set (WEBSOCKETPP_PATCH_VERSION 1)
+ set (WEBSOCKETPP_VERSION ${WEBSOCKETPP_MAJOR_VERSION}.${WEBSOCKETPP_MINOR_VERSION}.${WEBSOCKETPP_PATCH_VERSION})
+ 
+ if(POLICY CMP0048)