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.

strings/ctype.c

@@ -405,3 +405,23 @@ my_charset_is_8bit_pure_ascii(CHARSET_INFO *cs)
   }
   return 1;
 }
+
+
+/*
+  Shared function between conf_to_src and mysys.
+  Check if a 8bit character set is compatible with
+  ascii on the range 0x00..0x7F.
+*/
+my_bool
+my_charset_is_ascii_compatible(CHARSET_INFO *cs)
+{
+  uint i;
+  if (!cs->tab_to_uni)
+    return 1;
+  for (i= 0; i < 128; i++)
+  {
+    if (cs->tab_to_uni[i] != i)
+      return 0;
+  }
+  return 1;
+}