Backporting WL#3759 Optimize identifier conversion in client-server protocol

This patch provides performance improvements:
- send_fields() when character_set_results = latin1
  is now about twice faster for column/table/database
  names, consisting on ASCII characters.

Changes:

- Protocol doesn't use "convert" temporary buffer anymore,
  and converts strings directly to "packet".

- General conversion optimization: quick conversion
  of ASCII strings was added.

modified files:

include/m_ctype.h
- Adding a new flag.
- Adding a new function prototype

libmysqld/lib_sql.cc
- Adding quick conversion method for embedded library:
  conversion is now done directly to result buffer,
  without using a temporary buffer.

mysys/charset.c
- Mark all dynamic ucs2 character sets as non-ASCII
- Mark some dymamic 7bit and 8bit charsets as non-ASCII
  (for example swe7 is not fully ASCII compatible).

sql/protocol.cc
- Adding quick method to convert a string directly
  into protocol buffer, without using a temporary buffer.

sql/protocol.h
- Adding a new method prototype

sql/sql_string.cc
  Optimization for conversion between two ASCII-compatible charsets:
- quickly convert ASCII strings,
  switch to mc_wc->wc_mb method only when a non-ASCII character is met.
- copy four ASCII characters at once on i386

strings/conf_to_src.c
- Marking non-ASCII character sets with a flag.

strings/ctype-extra.c
- Regenerating ctype-extra.c by running "conf_to_src".

strings/ctype-uca.c
- Marking UCS2 character set as non-ASCII.

strings/ctype-ucs2.c
- Marking UCS2 character set as non-ASCII.

strings/ctype.c
- A new function to detect if a 7bit or 8bit character set
  is ascii compatible.

libmysqld/lib_sql.cc

@@ -1175,3 +1175,27 @@ int vprint_msg_to_log(enum loglevel level __attribute__((unused)),
   mysql_server_last_errno= CR_UNKNOWN_ERROR;
   return 0;
 }
+
+
+bool Protocol::net_store_data(const uchar *from, size_t length,
+                              CHARSET_INFO *from_cs, CHARSET_INFO *to_cs)
+{
+  uint conv_length= to_cs->mbmaxlen * length / from_cs->mbminlen;
+  uint dummy_error;
+  char *field_buf;
+  if (!thd->mysql)            // bootstrap file handling
+    return false;
+
+  if (!(field_buf= (char*) alloc_root(alloc, conv_length + sizeof(uint) + 1)))
+    return true;
+  *next_field= field_buf + sizeof(uint);
+  length= copy_and_convert(*next_field, conv_length, to_cs,
+                           (const char*) from, length, from_cs, &dummy_error);
+  *(uint *) field_buf= length;
+  (*next_field)[length]= 0;
+  if (next_mysql_field->max_length < length)
+    next_mysql_field->max_length= length;
+  ++next_field;
+  ++next_mysql_field;
+  return false;
+}