Security update for apache2 (important)

This update for apache2 fixes the following issues:

 * CVE-2018-1283:  when mod_session is configured to forward its session
   data to CGI applications (SessionEnv on, not the default), a remote
   user may influence their content by using a \"Session\" header leading
   to unexpected behavior [bsc#1086814].

 * CVE-2018-1301: due to an out of bound access after a size limit being
   reached by reading the HTTP header, a specially crafted request could
   lead to remote denial of service. [bsc#1086817]

 * CVE-2018-1303: a specially crafted HTTP request header could lead to
   crash due to an out of bound read while preparing data to be cached in
   shared memory.[bsc#1086813]

 * CVE-2017-15715: a regular expression could match '$' to a newline
   character in a malicious filename, rather than matching only the end
   of the filename. leading to corruption of uploaded files.[bsc#1086774]

 * CVE-2018-1312: when generating an HTTP Digest authentication
   challenge, the nonce sent to prevent reply attacks was not correctly
   generated using a pseudo-random seed. In a cluster of servers using a
   common Digest authentication configuration, HTTP requests could be
   replayed across servers by an attacker without detection. [bsc#1086775]

 * CVE-2017-15710: mod_authnz_ldap, if configured with
   AuthLDAPCharsetConfig, uses the Accept-Language header value to lookup
   the right charset encoding when verifying the user's credentials. If
   the header value is not present in the charset conversion table, a
   fallback mechanism is used to truncate it to a two characters value to
   allow a quick retry (for example, 'en-US' is truncated to 'en'). A
   header value of less than two characters forces an out of bound write
   of one NUL byte to a memory location that is not part of the string.
   In the worst case, quite unlikely, the process would crash which could
   be used as a Denial of Service attack. In the more likely case, this
   memory is already reserved for future use and the issue has no effect
   at all. [bsc#1086820]

 *  gensslcert: fall back to 'localhost' as hostname [bsc#1057406]