httpd: fix several bugs triggering by realtive path in -h DIR.

function                                             old     new   delta
handle_incoming_and_exit                            2657    2659      +2
send_cgi_and_exit                                    869     862      -7
parse_conf                                          1647    1626     -21
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 2/-28)             Total: -26 bytes

1 files changed, 4 insertions, 0 deletions

diff --git a/include/libbb.h b/include/libbb.h
index dfcc96d5b..281152f5f 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -938,6 +938,10 @@ int bb_ask_confirmation(void);
 
 extern int bb_parse_mode(const char* s, mode_t* theMode);
 
+/* Concatenate path and filename to new allocated buffer.
+ * Add "/" only as needed (no duplicate "//" are produced).
+ * If path is NULL, it is assumed to be "/".
+ * filename should not be NULL. */
 char *concat_path_file(const char *path, const char *filename);
 char *concat_subpath_file(const char *path, const char *filename);
 const char *bb_basename(const char *name);