playback-history-qt: Extract shareable code

Preparation work for a GTK port of this plugin.

Author: radioactiveman

src/playback-history-qt/Makefile

@@ -1,6 +1,7 @@
 PLUGIN = playback-history-qt${PLUGIN_SUFFIX}
 
-SRCS = playback-history.cc
+SRCS = ../playback-history/history-entry.cc \
+       playback-history.cc
 
 include ../../buildsys.mk
 include ../../extra.mk

src/playback-history-qt/meson.build

@@ -1,4 +1,5 @@
 shared_module('playback-history-qt',
+  '../playback-history/history-entry.cc',
   'playback-history.cc',
   dependencies: [audacious_dep, qt_dep, audqt_dep],
   name_prefix: '',