libgcc2's warning: implicit declaration of function `abort'

[Doug Evans]

When building gcc before libc has been installed, one gets
several warnings in libgcc2.

/samantha/gnu-build/m32r/bgcc/gcc/xgcc -B/samantha/gnu-build/m32r/bgcc/gcc/ -B/home/dje/gnu/rel/play/m32r-elf/bin/ -B/home/dje/gnu/rel/play/m32r-elf/lib/ -isystem /home/dje/gnu/rel/play/m32r-elf/include -isystem /home/dje/gnu/rel/play/m32r-elf/sys-include -O2  -DIN_GCC -DCROSS_COMPILE   -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -isystem ./include  -G 0 -g  -DIN_LIBGCC2 -D__GCC_FLOAT_NOT_NEEDED -Dinhibit_libc -I. -I. -I../../gcc/gcc -I../../gcc/gcc/. -I../../gcc/gcc/config -I../../gcc/gcc/../include  -msdata=sdata -DL_absvsi2 -c ../../gcc/gcc/libgcc2.c -o libgcc/./_absvsi2.o
../../gcc/gcc/libgcc2.c: In function `__absvsi2':
../../gcc/gcc/libgcc2.c:204: warning: implicit declaration of function `abort'

For the inhibit_libc case, what about adding a decl to tsystem.h?
malloc,free,atexit are already there.

For the !inhibit_libc case, tsystem.h includes stdlib.h so problem solved.

Is there any reason why the !inhibit_libc case in tsystem.h
provides malloc,free,atexit but not abort?