We introduced some new text styles but never used them in the default
style so far. To make them more user visible we have done following changes

Output Argument to italic
Declaration to bold
Local variable to dark blue which is different to Macros
Global variable to orange
Functions to water blue

Task-number: QTCREATORBUG-18151
Change-Id: If3f62f74795b5ae35a92db2ef6d5c48219c8ad18
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>