Qt optimization suggestion: replace bundled zlib with SIMD optimized zlib-ng

Hi

Now that coming 5.10 seems to include SIMD accelerated libjpeg-turbo  (https://bugreports.qt.io/browse/QTBUG-40091) maybe the default bundled zlib could be replaced with SIMD accelerated zlib-ng ?

From: https://github.com/Dead2/zlib-ng.git

On Linux building for X86/X86-64: 

./configure --prefix=/usr --libdir=/lib --zlib-compat && make && make install

And for ARM the following (and maybe gcc flags: -march=armv8-a+crc -mfpu=neon-fp-armv8 ???) are needed:

./configure --prefix=/usr --libdir=/lib --zlib-compat --acle --neon && make && make install

The QByteArray qcompress/uncompress functions need patching tought because they expect the uLong* (in vanilla zlib.h) while in the zlib-ng version of zlib.h they are size_t* for length arguments.

Sorry, forgot in the hurry to change the "Type" field from Bug to Suggestion