tests: add tests on logger tail functions (issue #1926)

doc/en/weechat_dev.en.adoc

@@ -448,6 +448,7 @@ WeeChat "core" is located in following directories:
 |          logger/                    | Root of unit tests for logger plugin.
 |             test-logger.cpp         | Tests: logger.
 |             test-logger-backlog.cpp | Tests: logger backlog.
+|             test-logger-tail.cpp    | Tests: logger tail functions.
 |          trigger/                   | Root of unit tests for trigger plugin.
 |             test-trigger.cpp        | Tests: triggers.
 |             test-trigger-config.cpp | Tests: trigger configuration.

doc/fr/weechat_dev.fr.adoc

@@ -450,6 +450,7 @@ Le cœur de WeeChat est situé dans les répertoires suivants :
 |          logger/                    | Racine des tests unitaires pour l'extension logger.
 |             test-logger.cpp         | Tests : logger.
 |             test-logger-backlog.cpp | Tests : backlog logger.
+|             test-logger-tail.cpp    | Tests : fonctions "tail".
 |          trigger/                   | Racine des tests unitaires pour l'extension trigger.
 |             test-trigger.cpp        | Tests : triggers.
 |             test-trigger-config.cpp | Tests : configuration trigger.

doc/ja/weechat_dev.ja.adoc

@@ -502,6 +502,8 @@ WeeChat "core" は以下のディレクトリに配置されています:
 // TRANSLATION MISSING
 |             test-logger-backlog.cpp | Tests: logger backlog.
 // TRANSLATION MISSING
+|             test-logger-tail.cpp    | Tests: logger tail functions.
+// TRANSLATION MISSING
 |          trigger/                   | Root of unit tests for trigger plugin.
 // TRANSLATION MISSING
 |             test-trigger.cpp        | Tests: triggers.

doc/sr/weechat_dev.sr.adoc

@@ -450,6 +450,8 @@ WeeChat „језгро” се налази у следећим директо
 |          logger/                    | Корен unit тестива за logger додатак.
 |             test-logger.cpp         | Тестови: logger.
 |             test-logger-backlog.cpp | Тестови: logger заостатак.
+// TRANSLATION MISSING
+|             test-logger-tail.cpp    | Tests: logger tail functions.
 |          trigger/                   | Корен unit тестова за окидач додатак.
 |             test-trigger.cpp        | Тестови: окидачи.
 |             test-trigger-config.cpp | Тестови: конфигурација окидача.