safe_strtoXX interface proved to be a bit unconvenient.

Remove it, introduce saner bb_strtoXX.
Saved ~350 bytes.

libbb/Kbuild

@@ -10,6 +10,7 @@ lib-y += ask_confirmation.o
 lib-y += bb_askpass.o
 lib-y += bb_do_delay.o
 lib-y += bb_pwd.o
+lib-y += bb_strtonum.o
 lib-y += change_identity.o
 lib-y += chomp.o
 lib-y += compare_string_array.o
@@ -67,7 +68,6 @@ lib-y += remove_file.o
 lib-y += restricted_shell.o
 lib-y += run_shell.o
 lib-y += safe_strncpy.o
-lib-y += safe_strtol.o
 lib-y += safe_write.o
 lib-y += setup_environment.o
 lib-y += sha1.o