Do not allow information separators in record label

While it is not explicitely mentioned in the ISO2709 standard, it does
seem to be a sensible to use information separators in the
implementation codes and system chars area of the record label.

This commit adds the relevant checks to the record label.

(cherry picked from commit 9bcc8fc)

Author: cboehme

metafacture-biblio/src/main/java/org/metafacture/biblio/iso2709/RecordBuilder.java

@@ -102,16 +102,14 @@ public void setRecordStatus(final char recordStatus) {
     public void setImplCodes(final char[] implCodes) {
         Require.notNull(implCodes);
         Require.that(implCodes.length == IMPL_CODES_LENGTH);
-        for (final char implCode : implCodes) {
-            Require.that(implCode < Iso646Constants.MAX_CHAR_CODE);
-        }
+        require7BitAscii(implCodes);
         label.setImplCodes(implCodes);
     }
 
-    public void setImplCode(final int index, final char value) {
+    public void setImplCode(final int index, final char implCode) {
         Require.that(0 <= index && index < IMPL_CODES_LENGTH);
-        Require.that(value < Iso646Constants.MAX_CHAR_CODE);
-        label.setImplCode(index, value);
+        require7BitAscii(implCode);
+        label.setImplCode(index, implCode);
     }
 
     public void setSystemChars(final char[] systemChars) {
@@ -121,10 +119,10 @@ public void setSystemChars(final char[] systemChars) {
         label.setSystemChars(systemChars);
     }
 
-    public void setSystemChar(final int index, final char value) {
+    public void setSystemChar(final int index, final char systemChar) {
         Require.that(0 <= index && index < SYSTEM_CHARS_LENGTH);
-        Require.that(value < Iso646Constants.MAX_CHAR_CODE);
-        label.setSystemChar(index, value);
+        require7BitAscii(systemChar);
+        label.setSystemChar(index, systemChar);
     }
 
     public void setReservedChar(final char reservedChar) {