"Since" tags in all API methods and types

[Aleksander Morgado]

Hey,

I've gone through the whole libqmi API and added "Since" tags so that
we know on which version each method/type was introduced.

For the code generated from the JSON database, I've set "since" JSON
keys as mandatory for all messages and TLVs: from now on when a new
message or TLV is added, it should specify a "since" tag with the next
major stable version where it will be released.

These tags will be visible in the gtk-doc generated documentation
(e.g. see the Since: 1.12 tag in the qmi_message_tlv_write_complete()
method: https://www.freedesktop.org/software/libqmi/libqmi-glib/latest/libqmi-glib-QmiMessage.html#qmi-message-tlv-write-complete).
The next release will have this tag for all API types and methods.

-- 
Aleksander
https://aleksander.es