Another nice cleanup from Larry. This adds a new last_char_is() function and

uses it to avoid possible buffer underruns whn strlen is zero, and avoid the
possible space-hogging inline of strlen() in several cases.
 -Erik

include/libbb.h

@@ -218,6 +218,7 @@ int klogctl(int type, char * b, int len);
 
 char *xgetcwd(char *cwd);
 char *concat_path_file(const char *path, const char *filename);
+int last_char_is(const char *s, const int c);
 
 typedef struct ar_headers_s {
 	char *name;