MKL is largely independent of compilers. But interfaces as defined by various standards change. MKL supports two interfaces - cdecl and Compaq Visual Fortran default, which is very similar to stdcall except in how strings are passed.
So, mkl_c.lib supports cdecl and mkl_s.lib supports CVF default.
All characters are to be passed by reference just like other scalars are since underneath is a routine that obeys Fortran rules.
If you use Microsoft tools, you should link to mkl_c.lib.