0030609: Coding - eliminate warnings issued by gcc 8.1.0

0030609: Coding - eliminate warnings issued by gcc 8.1.0

Warnings issued by gcc 8.1.0 are eliminated.
New function OSD_FunctionCast() is introduced to explicitly mark places where the conversion from the pointer to one function type to the pointer to another function type takes place and to suppress gcc warning "-Wcast-function-type" (introduced in gcc 8.1.0).