plugins: Add plugin which analyzes execmem denials
    
    The plugin reacts to all execmem AVC's, suggesting a possibility to
    switch a boolean if the access can be allowed by one, or report the
    issue when no boolean can allow the access.
    
    "Safe" version:
    type=AVC msg=audit(1475320275.871:1076): avc:  denied  { execmem } for
    pid=30139 comm="php-fpm" scontext=system_u:system_r:httpd_t:s0
    tcontext=system_u:system_r:httpd_t:s0 tclass=process permissive=1
    
    SELinux is preventing php-fpm from using the execmem access on a process.
    
    *****  Plugin allow_execmem (53.1 confidence) suggests   ************
    
    If you know why php-fpm needs to map a memory region that is both
    executable and writable and understand that this is a potential
    security problem.
    Then you can allow the mapping by switching one of the following
    booleans: httpd_execmem
    Do
    follow the advice of the catchall_boolean plugin, otherwise contact
    your security administrator and report this issue
    
    *****  Plugin catchall_boolean (42.6 confidence) suggests   **********
    
    If you want to allow httpd scripts and modules execmem/execstack
    Then you must tell SELinux about this by enabling the 'httpd_execmem'
    boolean. You can read 'httpd_selinux' man page for more details.
    Do
    setsebool -P httpd_execmem 1
    
    --------------------------------------------------------------------
    
    "Unsafe" version:
    type=AVC msg=audit(1475320275.871:1076): avc:  denied  { execmem } for
    pid=30139 comm="php-fpm" scontext=system_u:system_r:init_t:s0
    tcontext=system_u:system_r:init_t:s0 tclass=process permissive=1
    
    *****  Plugin allow_execmem (91.4 confidence) suggests   ************
    
    If this issue occurred during normal system operation.
    Then this alert could be a serious issue and your system could be
    compromised.
    Do
    contact your security administrator and report this issue
    
    --------------------------------------------------------------------
    
    Fixes:
       https://github.com/fedora-selinux/setroubleshoot/issues/55