Fix warnings compiling in maintainer mode.
Install DB/common.php and DB/mysql.php on "make install".
# We still have a warning from http_config.h:97. Rasmus? :-)
Introduced PECL - PHP Extension and Code Library (prounounced "picke"), in
the "pecl" subdir. "make install" will now install the database abstraction
layer in PREFIX/lib/php.
I hereby dedicate this part of PHP to my daughter-of-yesterday Malin. :-)