Bug#11216: 'show character set' describes latin1 incorrectly

Index.xml:
  Fixing latin1 comment:
  it is actually cp1252, not iso-8859-1
ctype_latin1.result:
  changeing test results accordingly.
ctype-latin1.c:
  Fixed to- and from-Unicode conversion maps
  for better Unicode round trip of undefined
  characters.

mysql-test/r/ctype_latin1.result

@@ -168,7 +168,7 @@ hex(a)	hex(@u:=convert(a using utf8))	hex(@l:=convert(@u using latin1))	a=@l
 7E	7E	7E	1
 7F	7F	7F	1
 80	E282AC	80	1
-81	3F	3F	0
+81	C281	81	1
 82	E2809A	82	1
 83	C692	83	1
 84	E2809E	84	1
@@ -180,10 +180,10 @@ hex(a)	hex(@u:=convert(a using utf8))	hex(@l:=convert(@u using latin1))	a=@l
 8A	C5A0	8A	1
 8B	E280B9	8B	1
 8C	C592	8C	1
-8D	3F	3F	0
+8D	C28D	8D	1
 8E	C5BD	8E	1
-8F	3F	3F	0
-90	3F	3F	0
+8F	C28F	8F	1
+90	C290	90	1
 91	E28098	91	1
 92	E28099	92	1
 93	E2809C	93	1
@@ -196,7 +196,7 @@ hex(a)	hex(@u:=convert(a using utf8))	hex(@l:=convert(@u using latin1))	a=@l
 9A	C5A1	9A	1
 9B	E280BA	9B	1
 9C	C593	9C	1
-9D	3F	3F	0
+9D	C29D	9D	1
 9E	C5BE	9E	1
 9F	C5B8	9F	1
 A0	C2A0	A0	1

sql/share/charsets/Index.xml

@@ -106,7 +106,7 @@ To make maintaining easier please:
 
 <charset name="latin1">
   <family>Western</family>
-  <description>ISO 8859-1 West European</description>
+  <description>cp1252 West European</description>
   <alias>csisolatin1</alias>
   <alias>iso-8859-1</alias>
   <alias>iso-ir-100</alias>

strings/ctype-latin1.c

@@ -108,6 +108,13 @@ static uchar sort_order_latin1[] = {
    
    - continue to pretend the latin1 character set is ISO 8859-1
    - actually allow the storage of euro etc. so it's actually cp1252
+
+  Also we'll map these five undefined cp1252 character:
+    0x81, 0x8D, 0x8F, 0x90, 0x9D
+  into corresponding control characters:
+     U+0081, U+008D, U+008F, U+0090, U+009D.
+  like ISO-8859-1 does. Otherwise, loading "mysqldump"
+  output doesn't reproduce these undefined characters.
 */
 
 unsigned short cs_to_uni[256]={
@@ -127,10 +134,10 @@ unsigned short cs_to_uni[256]={
 0x0068,0x0069,0x006A,0x006B,0x006C,0x006D,0x006E,0x006F,
 0x0070,0x0071,0x0072,0x0073,0x0074,0x0075,0x0076,0x0077,
 0x0078,0x0079,0x007A,0x007B,0x007C,0x007D,0x007E,0x007F,
-0x20AC,0x0000,0x201A,0x0192,0x201E,0x2026,0x2020,0x2021,
-0x02C6,0x2030,0x0160,0x2039,0x0152,0x0000,0x017D,0x0000,
-0x0000,0x2018,0x2019,0x201C,0x201D,0x2022,0x2013,0x2014,
-0x02DC,0x2122,0x0161,0x203A,0x0153,0x0000,0x017E,0x0178,
+0x20AC,0x0081,0x201A,0x0192,0x201E,0x2026,0x2020,0x2021,
+0x02C6,0x2030,0x0160,0x2039,0x0152,0x008D,0x017D,0x008F,
+0x0090,0x2018,0x2019,0x201C,0x201D,0x2022,0x2013,0x2014,
+0x02DC,0x2122,0x0161,0x203A,0x0153,0x009D,0x017E,0x0178,
 0x00A0,0x00A1,0x00A2,0x00A3,0x00A4,0x00A5,0x00A6,0x00A7,
 0x00A8,0x00A9,0x00AA,0x00AB,0x00AC,0x00AD,0x00AE,0x00AF,
 0x00B0,0x00B1,0x00B2,0x00B3,0x00B4,0x00B5,0x00B6,0x00B7,
@@ -161,10 +168,11 @@ unsigned char pl00[256]={
 0x68,0x69,0x6A,0x6B,0x6C,0x6D,0x6E,0x6F,
 0x70,0x71,0x72,0x73,0x74,0x75,0x76,0x77,
 0x78,0x79,0x7A,0x7B,0x7C,0x7D,0x7E,0x7F,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
-0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
+0x00,0x81,0x00,0x00,0x00,0x00,0x00,0x00,
+0x00,0x00,0x00,0x00,0x00,0x8D,0x00,0x8F,
+0x90,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
+0x00,0x00,0x00,0x00,0x00,0x9D,0x00,0x00,
+
 0xA0,0xA1,0xA2,0xA3,0xA4,0xA5,0xA6,0xA7,
 0xA8,0xA9,0xAA,0xAB,0xAC,0xAD,0xAE,0xAF,
 0xB0,0xB1,0xB2,0xB3,0xB4,0xB5,0xB6,0xB7,