findText: fix regression on case-insensitive search

introduced by commit 86326030f6989c79f8dd9e91cd4c249278cdbc49

The function to detect 7bit Ascii assumed the check was being
done on a plain C char type (1 byte length) whereas the passed
Unicode type is bigger (defined as unsigned int) and so can hold
larger values. So fix our detection for an Ascii7 char appropriately.

Fixes issue #743
1 file changed