QPdfDocument: make code locale-independent

The C toupper/tolower functions are locale-dependent. Given the right
locale (Türkiye, e.g.), tolower(I) is either

- ı (LATIN SMALL LETTER DOTLESS I; if representable in current charset)
- I (unchanged; if it isn't)

Both results are wrong for the present use-case, so use US-ASCII-only
QtMiscUtils::toAsciiLower() to side-step the issue.

Besides, feeding unfiltered char values into tolower() is UB. You'd
first have to cast to uchar:
https://en.cppreference.com/w/cpp/string/byte/tolower

Task-number: QTBUG-109235
Pick-to: 6.5 6.4
Change-Id: I57887581ba2e548e978223337d681124b30bf754
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions