s3: make better use of ccache by not including version.h in every C-file.

s3: make better use of ccache by not including version.h in every C-file.

version.h changes rather frequently. Since it is included via includes.h,
this means each C file will be a cache miss. This applies to the following
situations:

* When building a new package with a new Samba version

* building in a git branch after calling mkversion.sh
  after a new commit (i.e. virtually always)

This patch improves the situation in the following way:

* remove inlude "version.h" from includes.h

* Use samba_version_string() instead of SAMBA_VERSION_STRING
  in files that use no other macro from version.h instead of
  SAMBA_VERSION_STRING.

* explicitly include "version.h" in those files that use more
  macros from "version.h" than just SAMBA_VERSION_STRING.

Michael