Merge tag '2.0.6'

Release 2.0.6

diff --cc debian/libdtkcore-dev.install
index e5856ee015101bdc86dd7d7a9ff48cd6baddb133,ce9428eb94ff93be9b69fbdc158e1652e8d82147..4d84b84e27c0bab225d3597835fdd6cd12174e40
--- 1/debian/libdtkcore-dev.install
--- 2/debian/libdtkcore-dev.install
+++ b/debian/libdtkcore-dev.install
@@@ -1,4 -1,5 +1,5 @@@
 -usr/lib/*/lib*.so
  usr/include
 -usr/lib/*/pkgconfig/*.pc
 -usr/lib/dtk2/*
 +usr/include/*/qt5/QtXcb
 +usr/lib/*/libdtkcore.so
 +usr/lib/*/pkgconfig/dtkcore.pc
+ usr/lib/*/cmake/*/*.cmake