Replace string literals with QString::fromLatin1() expression
Replace string literals with QString::fromLatin1() expression

to avoid deprecated warning (since Qt 5.1.1)
Replaced fromLatin1() with QStringLiteral

Change-Id: I0602cbe905310796357af97c8310dad6346c5f73
Reviewed-by: Steven Ceuppens <5e748651f737dd57a9400119267c23838ccdc0c5@icloud.com>

remimixlr/QtWebsocket,SfietKonstantin/qtwebsockets,pixty/qtwebsockets,pixty/qtwebsockets