Rewrite table_is_system for clarity, extensibility

Previous version was a hot mess: casting strings to strings, using a
sentinel value to mark the end of an array, using a while loop where a for
loop was appropriate, nesting all function logic in one branch of an if
statement.  Why even.

This version is much cleaner, and it begins with a std::vector, which
means we can (in commits to follow) add elements to it based on
command-line options.

Author: piki

storage/innobase/dict/mem.cc

@@ -147,35 +147,27 @@ void dict_mem_table_free(dict_table_t *table) /*!< in: table */
 }
 
 /** System databases */
-static std::string innobase_system_databases[] = {
-    "mysql/", "information_schema/", "performance_schema/", ""};
+static std::vector<std::string> innobase_system_databases({
+    "mysql/", "information_schema/", "performance_schema/"
+});
 
 /** Determines if a table is a system table
 @param[in]  name  table_name
 @return true if table is system table */
-static bool dict_mem_table_is_system(const std::string name) {
+static bool dict_mem_table_is_system(const std::string &name) {
   /* Table has the following format: database/table and some system table are
   of the form SYS_* */
-  if (name.find('/') != std::string::npos) {
-    size_t table_len = name.length();
-
-    std::string system_db = std::string(innobase_system_databases[0]);
-    int i = 0;
-
-    while (system_db.compare("") != 0) {
-      size_t len = system_db.length();
-
-      if (table_len > len && name.compare(0, len, system_db) == 0) {
-        return true;
-      }
+  if (name.find('/') == std::string::npos) {
+    return true;
+  }
 
-      system_db = std::string(innobase_system_databases[++i]);
+  for (auto p : innobase_system_databases) {
+    if (name.length() > p.length() && name.compare(0, p.length(), p) == 0) {
+      return true;
     }
-
-    return false;
-  } else {
-    return true;
   }
+
+  return false;
 }
 
 /** Creates a table memory object.