On svn-auth-x509, follow-up to r1618575, minor tweaks.

* subversion/libsvn_subr/x509parse.c
  (equal): Switch to void type to avoid needing casts.
  (oids_equal): Remove casts.
  (starts_with): Fix indentation in declaration.

Suggested by: brane


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/svn-auth-x509@1618577 13f79535-47bb-0310-9956-ffa450edef68