Audit basename(1)

1) be stricter which number of arguments is accepted (1 or 2)
2) basename already returns a pointer to "." is argv[0] is ""
3) No need to check for *p != '/', because basename() only returns
   a string beginning with '/' which has length 1, so if strlen(p)
   == 1, the only way for suffix to be "evaluated" is for off to
   be > 0, being equal to suffix being "", but "" != "/".
4) don't calculate strlen twice for each string. Store it in a
   ssize_t and check if it's > 0.

README

@@ -7,9 +7,9 @@ across UNIX and UNIX-like systems.
 The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 '=' == implicit UTF-8 support, '|' == audited):
 
-   UTILITY         POSIX 2008 COMPLIANT         MISSING OPTIONS
-   -------         --------------------         ---------------
-=*  basename        yes                          none
+    UTILITY         POSIX 2008 COMPLIANT         MISSING OPTIONS
+    -------         --------------------         ---------------
+=*| basename        yes                          none
 =*  cal             yes                          none
 =*  cat             yes                          none
 =*  chgrp           yes                          none