GCC error code

warior@warior-desktop:~/john-1.6/src$ make linux-x86-mmx-elf
ln -sf x86-mmx.h arch.h
make ../run/john ../run/unshadow ../run/unafs ../run/unique \
JOHN_OBJS="DES_fmt.o DES_std.o BSDI_fmt.o MD5_fmt.o MD5_std.o BF_fmt.o BF_std.o AFS_fmt.o LM_fmt.o batch.o bench.o charset.o common.o compiler.o config.o cracker.o external.o formats.o getopt.o idle.o inc.o john.o list.o loader.o logger.o math.o memory.o misc.o options.o params.o path.o recovery.o rpp.o rules.o signals.o single.o status.o tty.o wordlist.o unshadow.o unafs.o unique.o x86.o" \
CFLAGS="-c -Wall -O2 -fomit-frame-pointer -m486"
make[1]: Entering directory `/home/warior/john-1.6/src'
gcc -c -Wall -O2 -fomit-frame-pointer -m486 -funroll-loops DES_fmt.c
DES_fmt.c:6:20: error: string.h: No such file or directory
DES_fmt.c:29: error: ‘NULL’ undeclared here (not in a function)
DES_fmt.c: In function ‘split’:
DES_fmt.c:121: warning: implicit declaration of function ‘memcpy’
DES_fmt.c:121: warning: incompatible implicit declaration of built-in function ‘memcpy’
DES_fmt.c:124: warning: incompatible implicit declaration of built-in function ‘memcpy’
DES_fmt.c: In function ‘set_key’:
DES_fmt.c:312: warning: incompatible implicit declaration of built-in function ‘memcpy’
DES_fmt.c: In function ‘get_key’:
DES_fmt.c:322: warning: incompatible implicit declaration of built-in function ‘memcpy’
make[1]: *** [DES_fmt.o] Chyba 1
make[1]: Leaving directory `/home/warior/john-1.6/src'
make: *** [linux-x86-mmx-elf] Chyba 2