core: added parameters log_engine_type and log_engine_data

- can be used to specify what logging engine to be used and its
  initialization data
- see readme of log_custom module for a same of usage

cfg.lex

@@ -290,6 +290,8 @@ LOGFACILITY	log_facility
 LOGNAME		log_name
 LOGCOLOR	log_color
 LOGPREFIX	log_prefix
+LOGENGINETYPE	log_engine_type
+LOGENGINEDATA	log_engine_data
 LISTEN		listen
 ADVERTISE	advertise|ADVERTISE
 ALIAS		alias
@@ -671,6 +673,8 @@ IMPORTFILE      "import_file"
 <INITIAL>{LOGNAME}	{ yylval.strval=yytext; return LOGNAME; }
 <INITIAL>{LOGCOLOR}	{ yylval.strval=yytext; return LOGCOLOR; }
 <INITIAL>{LOGPREFIX}	{ yylval.strval=yytext; return LOGPREFIX; }
+<INITIAL>{LOGENGINETYPE}	{ yylval.strval=yytext; return LOGENGINETYPE; }
+<INITIAL>{LOGENGINEDATA}	{ yylval.strval=yytext; return LOGENGINEDATA; }
 <INITIAL>{LISTEN}	{ count(); yylval.strval=yytext; return LISTEN; }
 <INITIAL>{ADVERTISE}	{ count(); yylval.strval=yytext; return ADVERTISE; }
 <INITIAL>{ALIAS}	{ count(); yylval.strval=yytext; return ALIAS; }

cfg.y

@@ -320,6 +320,8 @@ extern char *default_routename;
 %token LOGNAME
 %token LOGCOLOR
 %token LOGPREFIX
+%token LOGENGINETYPE
+%token LOGENGINEDATA
 %token LISTEN
 %token ADVERTISE
 %token ALIAS
@@ -775,6 +777,10 @@ assign_stm:
 	| LOGCOLOR EQUAL error { yyerror("boolean value expected"); }
 	| LOGPREFIX EQUAL STRING { log_prefix_fmt=$3; }
 	| LOGPREFIX EQUAL error { yyerror("string value expected"); }
+	| LOGENGINETYPE EQUAL STRING { _km_log_engine_type=$3; }
+	| LOGENGINETYPE EQUAL error { yyerror("string value expected"); }
+	| LOGENGINEDATA EQUAL STRING { _km_log_engine_data=$3; }
+	| LOGENGINEDATA EQUAL error { yyerror("string value expected"); }
 	| DNS EQUAL NUMBER   { received_dns|= ($3)?DO_DNS:0; }
 	| DNS EQUAL error { yyerror("boolean value expected"); }
 	| REV_DNS EQUAL NUMBER { received_dns|= ($3)?DO_REV_DNS:0; }