[glib] gcharset: Mention the environment variables queried by g_get_charset()

[Philip Withnall <pwithnall src gnome org>]

commit b6d1c128b3bfdd7b09f0e3598f41edad21a3c1cc
Author: Philip Withnall <withnall endlessm com>
Date:   Thu Feb 1 17:38:28 2018 +0000

    gcharset: Mention the environment variables queried by g_get_charset()
    
    Signed-off-by: Philip Withnall <withnall endlessm com>
    Reviewed-by: nobody

 glib/gcharset.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/glib/gcharset.c b/glib/gcharset.c
index 9d25db5..704ea13 100644
--- a/glib/gcharset.c
+++ b/glib/gcharset.c
@@ -166,6 +166,10 @@ charset_cache_free (gpointer data)
  * handle file names. It might be different from the character set
  * used by the C library's current locale.
  *
+ * On Linux, the character set is found by consulting nl_langinfo() if
+ * available. If not, the environment variables `LC_ALL`, `LC_CTYPE`, `LANG`
+ * and `CHARSET` are queried in order.
+ *
  * The return value is %TRUE if the locale's encoding is UTF-8, in that
  * case you can perhaps avoid calling g_convert().
  *