schema: Allow C as a valid locale

It should be permitted to set the "C.UTF-8" locale for minimal images
that are not preloaded with locales. The "C.UTF-8" locale has been
supported in Linux distributions for many years.

Author: Conan-Kudo

kiwi/schema/kiwi.rnc

@@ -27,7 +27,7 @@ namespace nul = ""
 safe-posix-name = xsd:token {pattern = "[a-zA-Z0-9_\-\.]+"}
 safe-posix-short-name = xsd:token {pattern = "[a-zA-Z0-9_\-\.]{1,32}"}
 ecma-119-achar-128-text = xsd:token {pattern = "[a-zA-Z0-9!-/:-?_ ]{1,128}"}
-locale-name = xsd:token {pattern = "(POSIX|[a-z]{2,3}_[A-Z]{2})(,[a-z]{2,3}_[A-Z]{2})*"}
+locale-name = xsd:token {pattern = "(C|POSIX|[a-z]{2,3}_[A-Z]{2})(,[a-z]{2,3}_[A-Z]{2})*"}
 mac-address-type = xsd:token {pattern = "([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}"}
 size-type = xsd:token {pattern = "(\d*|image)"}
 number-type = xsd:token {pattern = "\d+"}

kiwi/schema/kiwi.rng

@@ -38,7 +38,7 @@
   </define>
   <define name="locale-name">
     <data type="token">
-      <param name="pattern">(POSIX|[a-z]{2,3}_[A-Z]{2})(,[a-z]{2,3}_[A-Z]{2})*</param>
+      <param name="pattern">(C|POSIX|[a-z]{2,3}_[A-Z]{2})(,[a-z]{2,3}_[A-Z]{2})*</param>
     </data>
   </define>
   <define name="mac-address-type">