Add support for 64bit systems when looking for libmodsecurity

[omadjoudj]

Hi,
configure fails on 64bit system since find_libsec macros does not look in /usr and <?>/lib64/

NB. This also will help modsec v3 packaging.

[omadjoudj]

About the CI tests, it seems that httpd 2.4.27 tarballs have been moved somewhere else (returns 404).

$ export VER_APACHE=2.4.27
$ curl -I https://www.apache.org/dist/httpd/httpd-${VER_APACHE}.tar.gz 
HTTP/1.1 404 Not Found
Date: Sat, 28 Oct 2017 12:48:17 GMT
Server: Apache/2.4.7 (Ubuntu)
Content-Type: text/html; charset=iso-8859-1

[zimmerle]

Merged! Thanks!