add 70mai format (GPSBabel#1412)

* update upgrade for Qt6

1. change upgrade url method to https.  In the past this caused
problems on windows (GPSBabel#580, GPSBabel#587).  However, with Qt6 we are shipping
plugins for native TLS libraries (windows SChannel, macos Secure Transport)
as well as OpenSSL.  Qt will fall back on the native plugin if
required.
2. skip all the use count statistics if the user has disabled
them, i.e. babelData_.reportStatistics_ is false.
3. implement clazy QString allocation optimizations.
4. delete redundant QDateTime constructor.
5. use default initializers.
6. delete obsolete manual redirection code.
7. delete unused variable.

* add 70mai format.

* update serialization references for new format.

* handle null video file name with A500

* hold off on 70mai test until complete

* add 70mai test.

CMakeLists.txt

@@ -111,6 +111,7 @@ set(ALL_FMTS ${MINIMAL_FMTS}
   ozi.cc
   qstarz_bl_1000.cc
   random.cc
+  seventymai.cc
   shape.cc
   skytraq.cc
   subrip.cc
@@ -248,6 +249,7 @@ set(HEADERS
   qstarz_bl_1000.h
   random.h
   session.h
+  seventymai.h
   shape.h
   skytraq.h
   subrip.h
@@ -423,6 +425,7 @@ set(TESTS
   resample
   route_reverse
   serialization
+  seventymai
   shape
   simplify-relative
   simplify