Update changelog for 2.0.0~alpha2-1 release

debian/changelog

+php-phpdocumentor-reflection-common (2.0.0~alpha2-1) experimental; urgency=medium
+
+  * Upload alpha to experimental
+
+  [ Chuck Burgess ]
+  * update copyright, license blurb, and remove php version from docblocks;
+
+  [ David Prévot ]
+  * Update copyright (years)
+  * Move project repository to salsa.d.o
+  * Update Standards-Version to 4.1.3
+
+ -- David Prévot <taffit@debian.org>  Tue, 06 Mar 2018 15:25:03 -1000
+
 php-phpdocumentor-reflection-common (1.0.1-1) unstable; urgency=medium
 
   [ Jon Dufresne ]