Generate a tune up tone when WSPR band hopping for Tx periods

Previously a tune up  tone was not generated if the  first period on a
new band was  going to be a Tx  period, this is no longer  so and thus
allows low (or high) power tune tones as set up by the user. Note that
tune up tones are  still not sent for bands flagged as  Rx Only in the
band hopping  schedule, this  is to protect  active aerials  and avoid
unintended transmissions on unlicensed bands.

WSPR/WSPRBandHopping.cpp

@@ -473,7 +473,6 @@ auto WSPRBandHopping::next_hop (bool tx_enabled) -> Hop
 
       , frequencies_index >= 0               // new band
       && tx_enabled                          // transmit is allowed
-      && !tx_next                            // not going to Tx anyway
       && m_->bands_[4].testBit (band_index)  // tune up required
       && !m_->bands_[5].testBit (band_index) // not an Rx only band
 

WSPR/WSPRBandHopping.hpp

@@ -24,7 +24,8 @@ class QWidget;
 //
 //  Along with selecting bands a flag  indicating that a short tune up
 //  signal is  required for specified  bands before they are  used for
-//  receive.
+//  transmit or receive, unless they  are flagged as Rx Only (intended
+//  to protect Rx active aerials and non-licensed bands).
 //
 //  Provides a Qt property that holds  the Tx percentage which is used
 //  to generate a semi-randomized schedule of period to transmit. This