Added lineIsWhitespace function.

ZString.cpp

@@ -311,6 +311,19 @@ namespace coreutils {
       return len;
    }
 
+   bool ZString::lineIsWhitespace() {
+      char *end = data + length;
+      char *temp = cursor;
+      while(temp < end) {
+	 if(*temp == '\n')
+	   return true;
+	 if((*temp != ' ') && (*temp != '\t'))
+	   return false;
+	 ++temp;
+      }
+      return true;
+   }
+      
    ZString ZString::goeol() {
       bool set = false;
       char *temp = cursor;