Emit connector version in error log

[defanator]

Also, use the same string in msc_set_connector_info().

Ideally, "banner" should be printed in init module function [1], but in this case it won't appear if there are errors in ModSecurity configuration (evaluated by msc_init()), therefore I decided to put it into earlier configuration creation phase.

Example log (valid configuration):

root@vagrant:/# nginx
root@vagrant:/# cat /var/log/nginx/error.log 
2017/12/25 09:38:30 [notice] 13364#13364: ModSecurity-nginx v1.0.0
2017/12/25 09:38:30 [notice] 13364#13364: using the "epoll" event method
2017/12/25 09:38:30 [notice] 13364#13364: nginx/1.13.7
2017/12/25 09:38:30 [notice] 13364#13364: built by gcc 6.3.0 20170406 (Ubuntu 6.3.0-12ubuntu2) 
2017/12/25 09:38:30 [notice] 13364#13364: OS: Linux 4.10.0-30-generic
2017/12/25 09:38:30 [notice] 13364#13364: getrlimit(RLIMIT_NOFILE): 131072:131072
2017/12/25 09:38:30 [notice] 13365#13365: start worker processes
2017/12/25 09:38:30 [notice] 13365#13365: start worker process 13366

Example log (invalid configuration):

root@vagrant:/# nginx
nginx: [emerg] "modsecurity_rules_file" directive Rules error. File: /etc/nginx/modsec/modsecurity.conf. Line: 1. Column: 25. Invalid input:  NonexistentDirective 123 in /etc/nginx/nginx.conf:75
root@vagrant:/# cat /var/log/nginx/error.log 
2017/12/25 09:39:34 [notice] 13373#13373: ModSecurity-nginx v1.0.0
2017/12/25 09:39:34 [emerg] 13373#13373: "modsecurity_rules_file" directive Rules error. File: /etc/nginx/modsec/modsecurity.conf. Line: 1. Column: 25. Invalid input:  NonexistentDirective 123 in /etc/nginx/nginx.conf:75

[1] http://nginx.org/en/docs/dev/development_guide.html#core_modules

[defanator]

Also I thought that it would be useful to print ModSecurity information as well, and faced an issue with msc_who_am_i() extern C func. PR is here: owasp-modsecurity/ModSecurity#1640

(cc/ @zimmerle @victorhora)

[zimmerle]

Merged! Thanks.