#1 Improve "const correctness"

[Markus Elfring]

Would you like to apply the advices from the article
"http://en.wikipedia.org/wiki/Const_correctness" to
your sources?
I suggest to add the key word "const" to the type
specifiers for parameters like the following.

http://cvs.sourceforge.net/viewcvs.py/dbh/dbh_1.0/src/dbh_functions.h?rev=1.7&view=markup
archivo, ramas (function "DBH_create")
dir (function "DBH_settempdir")

http://cvs.sourceforge.net/viewcvs.py/dbh/dbh_1.0/src/dbh_s.c?rev=1.8&view=markup
archivo (function "DBH_open_S")