r more details.  It corresponds to the option
<code>--enable-osmesa</code>.

<!-- OSMesa specific options -->
<dl>
<dt><code>--with-osmesa-bits=BITS</code>
<dd><p> This option allows the size
of the color channel in bits to be specified. By default, an 8-bit
channel will be used, and the driver will be named libOSMesa. Other
options are 16- and 32-bit color channels, which will add the bit size
to the library name. For example, <code>--with-osmesa-bits=16</code>
will create the libOSMesa16 library with a 16