casper: convert macros to inline functions

In libcasper, the first argument to the function is a structure that
represents a connection to Casper. On systems without Casper, macros
are used to interpose the Casper functions to standard libc ones.
This may cause errors/warnings that the variable is not used.
With the inline function, there is no such problem.

I omitted this file in: 8c121177f063a187534dcd475b136c34474802cd