Add facility to disallow CAT commands while transmitting.

Some rigs either do not honour some CAT commands while transmitting or
interpret them  incorrectly. To  deal with this  a settings  option to
allow TX  frequency changes while  transmitting has been added  with a
default value of off.

Any UI actions that directly or indirectly change the TX frequency are
guarded according to this new option. As well as this band changes and
use of  the +2kHz check box  are disabled and guarded  respectively in
transmit mode.

Mode changes via the menu are now disabled while transmitting.

When TX frequency changes are allowed; frequency changes are correctly
implemented while in tune mode.

Double clicking  decodes while  transmitting now  correctly regenerate
and change the message sent on the fly.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@4349 ab8295b8-cf94-4d9e-aec4-7959e3be5d79

Modulator.cpp

@@ -58,7 +58,9 @@ void Modulator::start (unsigned symbolsLength, double framesPerSymbol, unsigned
   m_quickClose = false;
 
   m_symbolsLength = symbolsLength;
-  m_isym0 = std::numeric_limits<unsigned>::max (); // Arbitrary big number
+  m_isym0 = std::numeric_limits<unsigned>::max (); // Arbitrary big
+                                                   // number
+  m_frequency0 = 0.;
   m_addNoise = dBSNR < 0.;
   m_nsps = framesPerSymbol;
   m_frequency = frequency;
@@ -223,7 +225,7 @@ qint64 Modulator::readData (char * data, qint64 maxSize)
 
         for (unsigned i = 0; i < numFrames && m_ic <= i1; ++i) {
           isym = m_tuning ? 0 : m_ic / (4.0 * m_nsps); //Actual fsample=48000
-          if (isym != m_isym0) {
+          if (isym != m_isym0 || m_frequency != m_frequency0) {
             // qDebug () << "@m_ic:" << m_ic << "itone[" << isym << "] =" << itone[isym] << "@" << i << "in numFrames:" << numFrames;
 
             if(m_toneSpacing==0.0) {
@@ -233,6 +235,7 @@ qint64 Modulator::readData (char * data, qint64 maxSize)
             }
             m_dphi = m_twoPi * toneFrequency0 / m_frameRate;
             m_isym0 = isym;
+            m_frequency0 = m_frequency;
           }
 
           int j=m_ic/480;