[libcalamares] Add API for geographical lookup

- find a zone given lat, lon -- with a failing test and a bogus
  implementation.

src/libcalamares/locale/Tests.cpp

@@ -52,6 +52,7 @@ private Q_SLOTS:
     void testComplexZones();
     void testTZLookup();
     void testTZIterator();
+    void testLocationLookup();
 };
 
 LocaleTests::LocaleTests() {}
@@ -389,6 +390,15 @@ LocaleTests::testTZIterator()
     QCOMPARE( ( *zones.begin() )->zone(), QStringLiteral( "Abidjan" ) );
 }
 
+void
+LocaleTests::testLocationLookup()
+{
+    const CalamaresUtils::Locale::ZonesModel zones;
+
+    QVERIFY( zones.find( 50.0, 0.0 ) );
+    QCOMPARE( zones.find( 50.0, 0.0 )->zone(), QStringLiteral( "London" ) );
+}
+
 
 QTEST_GUILESS_MAIN( LocaleTests )
 

src/libcalamares/locale/TimeZone.cpp

@@ -316,6 +316,12 @@ ZonesModel::find( const QString& region, const QString& zone ) const
     return nullptr;
 }
 
+const TimeZoneData*
+ZonesModel::find( double latitude, double longitude ) const
+{
+    return nullptr;
+}
+
 ZonesModel::Iterator::operator bool() const
 {
     return 0 <= m_index && m_index < m_p->m_zones.count();

src/libcalamares/locale/TimeZone.h

@@ -128,6 +128,12 @@ public:
      */
     const TimeZoneData* find( const QString& region, const QString& zone ) const;
 
+    /** @brief Look up TZ data based on the location.
+     *
+     * Returns the nearest zone to the given lat and lon.
+     */
+    const TimeZoneData* find( double latitude, double longitude ) const;
+
     /** @brief Iterator for testing purposes
      *
      * This is primarily for testing, but who knows, it might be useful