Fix for Bug#40700: aclocal warnings for missing cache-id's

Just change mysql_foo to mysql_cv_foo for one cache-id variable name.  There
was only one bad variable name, present in 5.0 and 5.1, but not in the -pe
branch.

config/ac-macros/misc.m4

@@ -726,15 +726,15 @@ dnl ---------------------------------------------------------------------------
 
 dnl MYSQL_NEEDS_MYSYS_NEW
 AC_DEFUN([MYSQL_NEEDS_MYSYS_NEW],
-[AC_CACHE_CHECK([needs mysys_new helpers], mysql_use_mysys_new,
+[AC_CACHE_CHECK([needs mysys_new helpers], mysql_cv_use_mysys_new,
 [
 AC_LANG_PUSH(C++)
 AC_TRY_LINK([], [
 class A { public: int b; }; A *a=new A; a->b=10; delete a;
-], mysql_use_mysys_new=no, mysql_use_mysys_new=yes)
+], mysql_cv_use_mysys_new=no, mysql_cv_use_mysys_new=yes)
 AC_LANG_POP(C++)
 ])
-if test "$mysql_use_mysys_new" = "yes"
+if test "$mysql_cv_use_mysys_new" = "yes"
 then
   AC_DEFINE([USE_MYSYS_NEW], [1], [Needs to use mysys_new helpers])
 fi