Update enginebuffer.cpp

Prefer prefix operator
Update enginemaster.cpp

Iterator 'it' is reassigned with same value
Update treeitemmodel.cpp

No need to initialize variable 'success' as it is assigned a value afterwards in any case
Update itunesfeature.cpp

No need to assign variable 'track_reference' a value beforehand as it is assigned via line 691 in any case
Update legacyskinparser.cpp

No need to assign variable 'stylehack' an empty string as it is filled anyway afterwards
Update beatmap.cpp

Prefer prefix operator
Update wlabel.cpp

No need to initialze variable 'fonsize' as it is assigned a value in line 52 in any case
Update vampanalyser.cpp

No need to assign variable 'ftime1' a value as it is assigned in any case in line 363
Merge pull request #361 from midzer/master

code cosmetics and minor performance enhancements