Will Thompson authored Sep 20, 2018 and Philip Withnall committed Oct 01, 2018

The X-Flatpak-RenamedFrom key is used in .desktop files to identify past
names for the desktop file. It is defined to be a list of strings.
However, there was previously no correct way to retrieve a list of
strings from the GKeyFile wrapped by GDesktopAppInfo, short of
re-parsing the file with GKeyFile.

Note that doing something like:

    g_strsplit (g_desktop_app_info_get_string (...), ";", -1)

is not correct: the raw value "a\;b;" represents the one-element list
["a;b"], but g_key_file_get_string() rejects the sequence "\;", and so
g_desktop_app_info_get_string() returns NULL in this case. (Of course, a
.desktop file with a semicolon in its name is a pathological case.)

Add g_desktop_app_info_get_string_list(), a trivial wrapper around
g_key_file_get_string_list(), similar to g_desktop_app_info_get_string()
and co.

The change from g_key_file_free() to g_key_file_unref() in the test is
needed because g_key_file_free() clears the contents of the keyfile...