restore shadow.h independence

Commit ee5dce3365 made busybox require shadow.h from the toolchain even
if the config opted for the internal busybox implementation.  This makes
building with toolchains that lack shadow support impossible.  Since the
merge only saved us from duplicating a simple structure (whose ABI isn't
going to ever change), restore the logic for complete busybox shadow
independence by reverting that previous commit slightly.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

include/libbb.h

@@ -76,8 +76,13 @@
 #include <pwd.h>
 #include <grp.h>
 #if ENABLE_FEATURE_SHADOWPASSWDS
+# if !ENABLE_USE_BB_SHADOW
+/* If using busybox's shadow implementation, do not include the shadow.h
+ * header as the toolchain may not provide it at all.
+ */
 #  include <shadow.h>
 # endif
+#endif
 
 /* Some libc's forget to declare these, do it ourself */
 

include/shadow_.h

@@ -24,10 +24,18 @@
 
 PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
 
-/* This file is #included after #include <shadow.h>
+/* Structure of the password file */
- * We will use libc-defined structures, but will #define function names
+struct spwd {
- * so that function calls are directed to bb_internal_XXX replacements
+	char *sp_namp;          /* Login name */
- */
+	char *sp_pwdp;          /* Encrypted password */
+	long sp_lstchg;         /* Date of last change */
+	long sp_min;            /* Minimum number of days between changes */
+	long sp_max;            /* Maximum number of days between changes */
+	long sp_warn;           /* Number of days to warn user to change the password */
+	long sp_inact;          /* Number of days the account may be inactive */
+	long sp_expire;         /* Number of days since 1970-01-01 until account expires */
+	unsigned long sp_flag;  /* Reserved */
+};
 
 /* Paths to the user database files */
 #ifndef _PATH_SHADOW