Refactor svn_checksum_create() to avoid two switch statements.
Refactor svn_checksum_create() to avoid two switch statements.

* subversion/libsvn_subr/checksum.c
  (checksum_create):
    New static function that creates a svn_checksum_t * with
    everything set but the contents of the digest.
  (svn_checksum_create):
    Use the existing switch statement to get the digest size without
    needing DIGESTSIZE().  Use checksum_create().


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1327695 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion