Enable tests, fixing the existing ones to use the current API

This also involved building a static library for the application for
tests to link to. The main application executable also links to it.

meson.build

@@ -4,7 +4,11 @@ project(
     version: '1.0.10',
     license: 'GPLv3',
     meson_version: '>=0.49.0',
-    default_options: [ 'warning_level=1', 'buildtype=debugoptimized', 'c_std=gnu11' ],
+    default_options: [
+        'warning_level=1',
+        'buildtype=debugoptimized',
+        'c_std=gnu11'
+    ]
 )
 
 i18n = import('i18n')
@@ -43,3 +47,4 @@ subdir('protocols')
 subdir('eek')
 subdir('src')
 subdir('po')
+subdir('tests')