First part of fix for bug 8310 - toupper_ascii() is broken on big-endian systems

First part of fix for bug 8310 - toupper_ascii() is broken on big-endian systems

Remove
int toupper_ascii(int c);
int tolower_ascii(int c);
int isupper_ascii(int c);
int islower_ascii(int c);

and replace with their _m equivalents, as they are identical.
(cherry picked from commit 5b6a34128a0e0bc33c255dc53c9fb9fd8e6d34d8)