Fixes in charset related C++ code


configure.in:
  Make things to be easier managable
include/m_ctype.h:
  Hide some functions under conditional compilation
libmysql/Makefile.shared:
  Make things to be easier managable
sql/item_func.cc:
  Fixed that private member is not available in this context
sql/item_strfunc.cc:
  Fixed that private member is not available in this context
strings/Makefile.am:
  Make charset things to be easier managable
  Some fixes in charset C++ code
strings/ctype-big5.c:
  Hide some functions under conditional compilation
strings/ctype-czech.c:
  Hide some functions under conditional compilation
strings/ctype-euc_kr.c:
  Hide some functions under conditional compilation
strings/ctype-gb2312.c:
  Hide some functions under conditional compilation
strings/ctype-gbk.c:
  Hide some functions under conditional compilation
strings/ctype-latin1_de.c:
  Hide some functions under conditional compilation
strings/ctype-mb.c:
  Hide some functions under conditional compilation
strings/ctype-sjis.c:
  Hide some functions under conditional compilation
strings/ctype-tis620.c:
  Hide some functions under conditional compilation
strings/ctype-ujis.c:
  Hide some functions under conditional compilation