QByteArray::setNum: use the existing latin1 lowercasing table

Not sure this makes the code faster, but it removes two functions.

Change-Id: I5d0ee9389a794d80983efffd152d830da44b1bfe
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/tools/qbytearray.cpp

@@ -782,19 +782,6 @@ QByteArray qUncompress(const uchar* data, int nbytes)
 }
 #endif
 
-static inline bool qIsUpper(char c)
-{
-    return c >= 'A' && c <= 'Z';
-}
-
-static inline char qToLower(char c)
-{
-    if (c >= 'A' && c <= 'Z')
-        return c - 'A' + 'a';
-    else
-        return c;
-}
-
 /*!
     \class QByteArray
     \inmodule QtCore
@@ -4136,9 +4123,10 @@ QByteArray &QByteArray::setNum(double n, char f, int prec)
     QLocaleData::DoubleForm form = QLocaleData::DFDecimal;
     uint flags = QLocaleData::ZeroPadExponent;
 
-    if (qIsUpper(f))
+    char lower = latin1_lowercased[uchar(f)];
+    if (f != lower)
         flags |= QLocaleData::CapitalEorX;
-    f = qToLower(f);
+    f = lower;
 
     switch (f) {
         case 'f':