Actually, I don't know what's the difference between the FreeBSD port and
original package, so I can hardly be of any help here. Technically
speaking, "dispatch_tab" is a symbol in an extension module that
points to the dispatcher table for the functions provided by that
module. The symbol is looked up using libtool wrappers, which follow
certain conventions regarding public symbols in .so files (see
http://www.gnu.org/software/libtool/manual.html#Module-loaders-for-libltdl,
for the detailed description). For example, the actual symbol name for
"dispatch_tab" in mysql.so module is "mysql_LTX_dispatch_tab". If
FreeBSD's port of libltdl does not follow this convention, you will get
the `dispatch_tab not found' error.