Add Zotero.platformVersion and Zotero.platformMajorVersion
Add Zotero.platformVersion and Zotero.platformMajorVersion

platformVersion is a string that needs to be checked with
nsIVersionComparator. platformMajorVersion is an integer that can be
checked with > and < when the major Gecko version is enough.

retorquere/zotero,gracile-fr/zotero,gracile-fr/zotero,LinuxMercedes/zotero,retorquere/zotero,rmzelle/zotero,LinuxMercedes/zotero,robamler/zotero,hoehnp/zotero,egh/zotero,LinuxMercedes/zotero,sendecomp/zotero,rmzelle/zotero,egh/zotero,sendecomp/zotero,hoehnp/zotero,sendecomp/zotero,robamler/zotero,egh/zotero,retorquere/zotero,fbennett/zotero,adunning/zotero,aurimasv/zotero,adunning/zotero,hoehnp/zotero,rmzelle/zotero,gracile-fr/zotero,adunning/zotero,robamler/zotero