[QBS] Qt, QtCreator and cpp.systemIncludePaths

[at-2500]

Hi,

I found that the Qt QBS module uses cpp.includePaths to add its include 
path to the compiler flags, while it should use cpp.systemIncludePaths.
Why? Paths in cpp.systemIncludePaths are added to e.g. clang using 
-isystem/path/you/added (in gcc it uses the -I flag instead of -i). The 
system flag prevents the compiler from generating warnings for the 
included header files. This means that currently, if there is a 
unnecessary semicolon in a Qt header and you push your projects warning 
level to extra extra high, The Qt header with the extra semicolon will 
actually throw warnings in your compilers output, which is quite annoying.
This is fixable very easily.

Also, I found that QtCreator doesn't add the cpp.systemIncludePaths to 
the internal searchpaths for autocompletion of the #include statement 
etc. This also prevents going into the header file using F2. 
cpp.includePaths are searched.

Thank you for your attention.
Jan Rudolph