Include the failed regexp pattern in the log output.

[cfi-gb]

This helps to debug VTs like e.g.:

/opt/greenbone/feed/plugins/2018/gb_sensitive_file_disclosures_http.nasl)(http_keepalive.inc:912) In function 'http_vuln_check()': egrep() : regcomp() failed

not directly calling the regexp NASL functions and using multiple regular expressions.

Testing NASL script:

pattern = "{1,2";
string = "test";

egrep(string:string, pattern:pattern);
ereg(string:string, pattern:pattern);
eregmatch(string:string, pattern:pattern);

Before:

lib  nasl-Message: 07:32:25.508: [12232](regxp.nasl:4) egrep() : regcomp() failed

lib  nasl-Message: 07:32:25.508: [12232](regxp.nasl:5) ereg() : regcomp() failed

lib  nasl-Message: 07:32:25.508: [12232](regxp.nasl:6) regmatch() : regcomp() failed

Afterwards:

lib  nasl-Message: 07:32:25.508: [12232](regxp.nasl:4) egrep() : regcomp() failed for pattern '{1,2'.

lib  nasl-Message: 07:32:25.508: [12232](regxp.nasl:5) ereg() : regcomp() failed for pattern '{1,2'.

lib  nasl-Message: 07:32:25.508: [12232](regxp.nasl:6) regmatch() : regcomp() failed for pattern '{1,2'.