cmake: Use cmake >= 3.5, add project setup.

Cmake made major changes in the 2.x -> 3.0 switch, keeping the 2.x
compatiblity just isn't worth it. Since serial anyway doesn't build on
versions before xenial, use xenial's cmake at 3.5 as baseline.

Cherry-pick from PR wjwwood#231

 Conflicts:
	CMakeLists.txt
 Author:    Alec Leamas <leamas.alec@gmail.com>
 Date:      Tue Sep 22 13:08:46 2020 +0200

Gbp-Pq: Name 0001-cmake-Use-cmake-3.5-add-project-setup.patch
Signed-off-by: Alex Moriarty <alex.moriarty@picknik.ai>

CMakeLists.txt

@@ -1,5 +1,11 @@
-cmake_minimum_required(VERSION 2.8.12)
-project(serial)
+cmake_minimum_required(VERSION 3.5.0)
+
+# General setup
+project(serial
+    VERSION 1.2.1
+    DESCRIPTION "Cross-platform, Serial Port library written in C++"
+    HOMEPAGE_URL "http://wjwwood.io/serial/"
+)
 
 if(APPLE)
     find_library(IOKIT_LIBRARY IOKit)