Re-factored the sockets interface to be easily replaced by F90 version

Defined a module interface for write/readbuffer and some wrappers that 
convert F90 types in such a form they can be passed as a "void *"



git-svn-id: svn://svn.code.sf.net/p/cp2k/code/trunk@14077 bac0169d-1eea-4375-b5f6-f89d2ced9994