Add work-around for Cisco Jabber language tags

Thanks to Holger for spotting this

Author: zinid

c_src/lang.abnf

@@ -8,6 +8,7 @@ langtag       = language
                  *("-" variant)
                  *("-" extension)
                  ["-" privateuse]
+		 ["." encoding]
 
 language      = 2*3ALPHA            ; shortest ISO 639 code
                  ["-" extlang]       ; sometimes followed by
@@ -38,6 +39,8 @@ singleton     = DIGIT               ; 0 - 9
 
 privateuse    = "x" 1*("-" (1*8alphanum))
 
+encoding      = "UTF-8"             ; work-around for Cisco Jabber
+
 grandfathered = irregular           ; non-redundant tags registered
                / regular             ; during the RFC 3066 era
 

c_src/lang.rl

@@ -1,4 +1,4 @@
-# Generated by abnfc at Wed May 30 08:31:04 2018
+# Generated by abnfc at Mon Dec 10 17:57:16 2018
 # Output file: lang.rl
 # Sources:
 # 	core
@@ -33,7 +33,8 @@
 	singleton = DIGIT | 0x41..0x57 | 0x59..0x5a | 0x61..0x77 | 0x79..0x7a;
 	extension = singleton ( "-" alphanum{2,8} )+;
 	privateuse = "x"i ( "-" alphanum{1,8} )+;
-	langtag = language ( "-" script )? ( "-" region )? ( "-" variant )* ( "-" extension )* ( "-" privateuse )?;
+	encoding = "UTF-8"i;
+	langtag = language ( "-" script )? ( "-" region )? ( "-" variant )* ( "-" extension )* ( "-" privateuse )? ( "." encoding )?;
 	irregular = "en-GB-oed"i | "i-ami"i | "i-bnn"i | "i-default"i | "i-enochian"i | "i-hak"i | "i-klingon"i | "i-lux"i | "i-mingo"i | "i-navajo"i | "i-pwn"i | "i-tao"i | "i-tay"i | "i-tsu"i | "sgn-BE-FR"i | "sgn-BE-NL"i | "sgn-CH-DE"i;
 	regular = "art-lojban"i | "cel-gaulish"i | "no-bok"i | "no-nyn"i | "zh-guoyu"i | "zh-hakka"i | "zh-min"i | "zh-min-nan"i | "zh-xiang"i;
 	grandfathered = irregular | regular;