shells: do not frocibly enable test, echo and kill _applets_,

just build relevant source and use xxx_main functions.
build system: add a special case when we have exactly one applet enabled
(makes "true", "false", "basename" REALLY tiny).
getopt32: do not use stdio.

function                                             old     new   delta
getopt32                                            1385    1412     +27
make_device                                         1187    1200     +13
basename_main                                        120     127      +7
tcpudpsvd_main                                      1922    1926      +4
testcmd                                                5       -      -5
echocmd                                                5       -      -5
fuser_main                                          1243    1231     -12
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 4/1 up/down: 51/-22)             Total: 29 bytes

2 files changed, 7 insertions, 13 deletions

diff --git a/include/busybox.h b/include/busybox.h
index cad45ac00..0c44d2f51 100644
--- a/include/busybox.h
+++ b/include/busybox.h
@@ -59,9 +59,6 @@ extern const uint8_t applet_install_loc[];
 /* Length of these names has effect on size of libbusybox
  * and "individual" binaries. Keep them short.
  */
-void lbb_prepare(const char *applet
-        USE_FEATURE_INDIVIDUAL(, char **argv)
-        ) MAIN_EXTERNALLY_VISIBLE;
 #if ENABLE_BUILD_LIBBUSYBOX
 #if ENABLE_FEATURE_SHARED_BUSYBOX
 int lbb_main(char **argv) EXTERNALLY_VISIBLE;
diff --git a/include/libbb.h b/include/libbb.h
index edf27c6d5..202574adb 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -848,23 +848,20 @@ extern void bb_verror_msg(const char *s, va_list p, const char *strerr);
 
 /* applets which are useful from another applets */
 int bb_cat(char** argv);
-int echo_main(int argc, char** argv) MAIN_EXTERNALLY_VISIBLE;
-int test_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int kill_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-#if ENABLE_ROUTE
-void bb_displayroutes(int noresolve, int netstatfmt);
-#endif
+/* If shell needs them, these three "exist" even if not enabled as applets */
+int echo_main(int argc, char** argv) USE_ECHO(MAIN_EXTERNALLY_VISIBLE);
+int test_main(int argc, char **argv) USE_TEST(MAIN_EXTERNALLY_VISIBLE);
+int kill_main(int argc, char **argv) USE_KILL(MAIN_EXTERNALLY_VISIBLE);
 int chown_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-#if ENABLE_GUNZIP
 int gunzip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-#endif
-#if ENABLE_BUNZIP2
 int bunzip2_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-#endif
 int bbunpack(char **argv,
         char* (*make_new_name)(char *filename),
         USE_DESKTOP(long long) int (*unpacker)(void)
 );
+#if ENABLE_ROUTE
+void bb_displayroutes(int noresolve, int netstatfmt);
+#endif
 
 
 /* Networking */