localcharset: update support for OpenBSD

[Bruno Haible]

In recent OpenBSD (at least OpenBSD 6.0 to 6.5), in the "C" locale,
nl_langinfo (CODESET) returns "US-ASCII", no longer "646". This needs
to be mapped to the GNU canonical name, in module 'localcharset'.


2019-12-22  Bruno Haible  <address@hidden>

        localcharset: Update support for OpenBSD.
        * lib/localcharset.c (alias_table): Map "US-ASCII" to "ASCII".

diff --git a/lib/localcharset.c b/lib/localcharset.c
index eec8dd1..ffc0d8f 100644
--- a/lib/localcharset.c
+++ b/lib/localcharset.c
@@ -150,7 +150,8 @@ static const struct table_entry alias_table[] =
     { "ISO8859-2",  "ISO-8859-2" },
     { "ISO8859-4",  "ISO-8859-4" },
     { "ISO8859-5",  "ISO-8859-5" },
-    { "ISO8859-7",  "ISO-8859-7" }
+    { "ISO8859-7",  "ISO-8859-7" },
+    { "US-ASCII",   "ASCII" }
 #   define alias_table_defined
 #  endif
 #  if defined __APPLE__ && defined __MACH__                 /* Mac OS X */