Only cache relevant records to avoid additional overhead on network (closes #20).

Don't remove service when PTR record expires

Fix compilation warnings

Signed-off-by: Patrick Jo Pereira <patrickelectric@gmail.com>

Signed-off-by: Patrick Jo Pereira <patrickelectric@gmail.com>

Defined in: Include/10.0.14393.0/um/combaseapi.h#L193
Signed-off-by: Patrick Jo Pereira <patrickelectric@gmail.com>

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Modernize by replacing foreach with ranged-for.

Use QRandomGenerator for Qt >= 5.15.

Compiling with Qt5.15 gives a warning that `qrand` is deprecated. It suggests using `QRandomGenerator` instead, which is done here.

Only include PTR records that correspond to the query target

This avoids creating massive PTR queries containing all PTR records ever received

Fix new/delete mismatch caught by ASAN.

Fix the Resolver example in the docs to use the correct name

Correct QMDNSENGINE_EXPORT when BUILD_SHARED_LIBS is undefined