Fix missing includes in libbsd

This makes it compile with -Werror.

build/jam/ArchitectureRules

@@ -673,6 +673,7 @@ rule ArchitectureSetupWarnings architecture
 	EnableWerror src bin package ;
 	EnableWerror src bin package_repo ;
 	EnableWerror src bin pkgman ;
+	EnableWerror src libs bsd ;
 	EnableWerror src apps ;
 	EnableWerror src kits ;
 	EnableWerror src preferences ;

src/libs/bsd/fgetln.c

@@ -9,6 +9,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 
 #define LINE_LENGTH 4096

src/libs/bsd/getpass.c

@@ -9,6 +9,7 @@
 
 #include <stdbool.h>
 #include <stdio.h>
+#include <string.h>
 #include <termios.h>
 #include <unistd.h>