[FIX] Fix unknown variable compilation error

 * when all debug flags are activated, this error
   was occuring

Change-Id: I677c9d3b9071592c66bafb1de1ec4c7db838b94e
[FIX] Improve pdok copy from/to pdo functions

Move pdok copy functions from a seperate file
(EplPdokCopy[Direct,Endian].c) back to EplPdok.c!
Introduce the switch EPL_DLL_PDOK_COPY_DIRECT to
enable/disable PDO copy without endian conversion.

This improves performance during mapping as the pdo
copy functions can be inlined by the compiler.
(Auto inline only works on static functions!)

Change-Id: Id86d1d373536d3b3dcb19727ccac867227c5ba86