implement reference counted strings

- on glib >=2.58, use the implementation provided by glib
- otherwise, a hash table will contain the strings

src/core/meson.build

@@ -43,6 +43,7 @@ libcore_a = static_library('core',
     'queries.c',
     'rawlog.c',
     'recode.c',
+    'refstrings.c',
     'servers-reconnect.c',
     'servers-setup.c',
     'servers.c',
@@ -114,6 +115,7 @@ install_headers(
     'queries.h',
     'rawlog.h',
     'recode.h',
+    'refstrings.h',
     'servers-reconnect.h',
     'servers-setup.h',
     'servers.h',