fix opencv-XXX.pc.cmake.in and core/cvdef.h

This pull request contains 2 minor changes:
1. using "static" to force inlineing of a function breaks builds with -Wall -Werror (specifically -Wunused-function). Better use
```__attribute__((always_inline))``` when gcc is used
2. The .pc template only contains adds the "opencv" directory to the included paths. "opencv2" should also be included