Work around another Doxygen::Filter::Perl issue

The 'optional' attribute of function parameters is documented but not implemented?!

FIJI/Connection.pm

@@ -20,7 +20,7 @@ use FIJI::AnySerialPort;
 # @brief Initiate the given serial port and this abstraction.
 #
 # \param portname The path to the device file of the port.
-# \param baudrate optional The baudrate to use.
+# \param baudrate (optional) The baudrate to use.
 #
 # \returns a FIJI::Connection object, or undef if non could be obtained.
 sub init {
@@ -215,8 +215,8 @@ sub sanitize_config {
 #
 # \param config_ref a reference to a hash representing a FIJI configuration (see \ref sanitize_config).
 # \param timeout An approximate(!) timeout for the whole operation.
-# \param block_till_ready optional Normally the function immediately starts to transmit the new configuration. If this parameter is defined and non-zero the function first waits for a READY message (up to the timeout).
-# \param wait_for_ready optional Normally the function returns immediately after the CONF_DONE message is received. If this parameter is defined and non-zero the function additionally waits for a READY/UNDERRUN message.
+# \param block_till_ready (optional) Normally the function immediately starts to transmit the new configuration. If this parameter is defined and non-zero the function first waits for a READY message (up to the timeout).
+# \param wait_for_ready (optional) Normally the function returns immediately after the CONF_DONE message is received. If this parameter is defined and non-zero the function additionally waits for a READY/UNDERRUN message.
 #
 # \returns 0 on success
 sub send_config {
@@ -399,7 +399,7 @@ sub send_config {
 #
 # \param port An initialized AnySerialPort port object
 # \param str_ref A reference to the payload string
-# \param timeout optional Approximate(!) timeout in ms. Unsupported on Unix.
+# \param timeout (optional) Approximate(!) timeout in ms. Unsupported on Unix.
 #
 # \returns the number of bytes actually transmitted
 sub _send_bitstream {
@@ -448,8 +448,8 @@ sub _send_bitstream {
 #
 # \param port An initialized AnySerialPort port object
 # \param todo The number of bytes to read
-# \param timeout optional Approximate(!) timeout for a reply in ms
-# \param out_ref optional An array reference to store (append) all read bytes
+# \param timeout (optional) Approximate(!) timeout for a reply in ms
+# \param out_ref (optional) An array reference to store (append) all read bytes
 #
 # \returns 0 on success
 sub _rcv_bitstream {