How to set up Qt in Dev-c++?

How to set up Qt to work with Dev-C++?

I have set up these environment variables so far:

QTDIR = D:\Qt\4.3.4\
INCLUDE = D:\Qt\4.3.4\include
PATH is extended with ;D:\Qt\4.3.4\bin;D:\Dev-Cpp\bin
QMAKESPEC = I don't know what to write here???

So far Dev-c++ compiles programs only if include like this:

#include <QApplication.h>

, but .h extension is not needed in Linux and it sould not be needed in Dev-c++ to.
Dev-c++ complains mainly that header files are not found.

absence of the .h is not guaranteed to work. use the .h as it is best practices since an extensionless file is of indeterminate type. Someone's had their collective heads up their arses when they thought of removing the .h extension from the standard. Next they will remove the .cpp from the source files, its just dumb and serves no purpose whatsoever.