settings: Add support for multi-line strings

Unterminated strings are now an error.

src/libstrongswan/settings/settings_lexer.l

@@ -119,16 +119,11 @@ static void include_files(parser_helper_t *ctx);
 <str>{
 	"\""				|
 	<<EOF>>				|
-	\n					|
 	\\					{
 		if (!streq(yytext, "\""))
 		{
-			if (streq(yytext, "\n"))
-			{	/* put the newline back to fix the line numbers */
-				unput('\n');
-				yy_set_bol(0);
-			}
 			PARSER_DBG1(yyextra, "unterminated string detected");
+			return STRING_ERROR;
 		}
 		if (yy_top_state(yyscanner) == inc)
 		{	/* string include */
@@ -148,7 +143,7 @@ static void include_files(parser_helper_t *ctx);
 	\\t     yyextra->string_add(yyextra, "\t");
 	\\\r?\n /* merge lines that end with EOL characters */
 	\\.     yyextra->string_add(yyextra, yytext+1);
-	[^\\\n"]+			{
+	[^\\"]+			{
 		yyextra->string_add(yyextra, yytext);
 	}
 }

src/libstrongswan/settings/settings_parser.y

@@ -79,7 +79,7 @@ static int yylex(YYSTYPE *lvalp, parser_helper_t *ctx)
 	struct kv_t *kv;
 }
 %token <s> NAME STRING
-%token NEWLINE
+%token NEWLINE STRING_ERROR
 
 /* ...and other symbols */
 %type <s> value valuepart