Added GeoClue2 privacy item

Rebased onto current master and fixed the privacy module build:
- privacy_item.hpp no longer includes privacy.hpp (it does not use the
  Privacy class); this broke the circular include that left PrivacyItem
  undeclared when privacy.hpp was reached first from privacy_item.cpp.
- privacy_item.cpp now includes gtkmm/label.h explicitly, since Gtk::Label
  was previously only pulled in transitively via privacy.hpp.

resources/icons/waybar-privacy-location-symbolic.svg

@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" height="16px" viewBox="0 0 16 16" width="16px"><path d="m 13.703125 1.046875 c -1.691406 0.5625 -4.636719 2.054687 -7.273437 3.4375 c -2.636719 1.382813 -4.898438 2.636719 -4.898438 2.636719 c -0.898438 0.503906 -0.542969 1.875 0.488281 1.875 h 5 v 5 c 0 1.03125 1.371094 1.386718 1.871094 0.488281 c 0 0 1.257813 -2.261719 2.640625 -4.898437 c 1.382812 -2.636719 2.875 -5.582032 3.4375 -7.273438 c 0.261719 -0.78125 -0.484375 -1.527344 -1.265625 -1.265625 z m 0 0" fill="#222222"/></svg>

resources/icons/waybar_icons.gresource.xml

@@ -4,5 +4,6 @@
     <file preprocess="xml-stripblanks">waybar-privacy-audio-input-symbolic.svg</file>
     <file preprocess="xml-stripblanks">waybar-privacy-audio-output-symbolic.svg</file>
     <file preprocess="xml-stripblanks">waybar-privacy-screen-share-symbolic.svg</file>
+    <file preprocess="xml-stripblanks">waybar-privacy-location-symbolic.svg</file>
   </gresource>
 </gresources>

resources/style.css

@@ -325,3 +325,7 @@ label:focus {
 #privacy-item.audio-out {
     background-color: #0069d4;
 }
+
+#privacy-item.location {
+    background-color: #00afff;
+}