Remove `using namespace std` to fix building with mingw-w64

Using `using namespace std;` is a bad practice, especially in header files
as it can lead to name collisions. In this case `std::byte` (from C++ 17)
collided with `typedef unsigned char byte` (from the Windows header
`rpcndr.h`) leading to many build errors.

src/MidiFile.cpp

@@ -80,7 +80,7 @@ void CMidiFile::openMidiFile(const std::string &filename)
         m_file.close();
     m_file.clear();  // clear any errors
 
-    m_file.open(filename.c_str(), ios_base::in | ios_base::binary);
+    m_file.open(filename.c_str(), std::ios_base::in | std::ios_base::binary);
     if (m_file.fail() == true)
     {
         QMessageBox::warning(nullptr, QMessageBox::tr("MIDI File Error"),
@@ -98,12 +98,12 @@ void CMidiFile::rewind()
 {
     m_numberOfTracks = 0;
     dword_t trackLength;
-    streampos filePos;
+    std::streampos filePos;
 
     midiError(SMF_NO_ERROR);
     m_ppqn = DEFAULT_PPQN;
 
-    m_file.seekg (0, ios::beg);
+    m_file.seekg (0, std::ios::beg);
 
     const auto ntrks = readHeader();
     if (ntrks == 0)
@@ -137,8 +137,8 @@ void CMidiFile::rewind()
             break;
         }
         //now move onto the next track
-        filePos += static_cast<streamoff>(trackLength);
-        m_file.seekg (filePos, ios::beg);
+        filePos += static_cast<std::streamoff>(trackLength);
+        m_file.seekg (filePos, std::ios::beg);
     }
     m_songTitle = m_tracks[0]->getTrackName();
     initMergedEvents();

src/MidiFile.h

@@ -36,8 +36,6 @@
 #include "Merge.h"
 
 #define DEFAULT_PPQN        96      /* Standard value for pulse per quarter note */
-
-using namespace std;
 #define MAX_TRACKS  40
 
 // Reads data from a standard MIDI file
@@ -72,7 +70,7 @@ private:
     bool checkMidiEventFromStream(int streamIdx);
     CMidiEvent fetchMidiEventFromStream(int streamIdx);
     void midiError(midiErrors_t error) {m_midiError = error;}
-    fstream m_file;
+    std::fstream m_file;
     static int m_ppqn;
     midiErrors_t m_midiError;
     CMidiTrack* m_tracks[MAX_TRACKS];

src/MidiTrack.cpp

@@ -41,7 +41,7 @@
 
 int CMidiTrack::m_logLevel;
 
-CMidiTrack::CMidiTrack(fstream& file, int no) :m_file(file), m_trackNumber(no)
+CMidiTrack::CMidiTrack(std::fstream& file, int no) :m_file(file), m_trackNumber(no)
 {
     m_trackEventQueue = nullptr;
     m_savedRunningStatus = 0;
@@ -122,11 +122,11 @@ dword_t CMidiTrack::readVarLen()
     return ( value );
 }
 
-string CMidiTrack::readTextEvent()
+std::string CMidiTrack::readTextEvent()
 {
     dword_t length;
 
-    string text;
+    std::string text;
     length = readVarLen();
     if (length >= 1000)
     {
@@ -250,7 +250,7 @@ void CMidiTrack::readKeySignatureEvent()
 
 void CMidiTrack::readMetaEvent(byte_t type)
 {
-    string text;
+    std::string text;
     __dt(dword_t data);
 
     if (failed() == true)
@@ -517,7 +517,7 @@ void CMidiTrack::decodeTrack()
 {
     CMidiEvent event;
 
-    m_file.seekg(m_filePos, ios::beg);
+    m_file.seekg(m_filePos, std::ios::beg);
     while (true)
     {
         if (m_trackLengthCounter== 0)

src/MidiTrack.h

@@ -34,8 +34,6 @@
 #include "Queue.h"
 #include "MidiEvent.h"
 
-using namespace std;
-
 typedef enum
 {
     SMF_NO_ERROR,
@@ -54,7 +52,7 @@ typedef unsigned long dword_t;
 class CMidiTrack
 {
 public:
-    CMidiTrack(fstream& file, int no);
+    CMidiTrack(std::fstream& file, int no);
 
     ~CMidiTrack()
     {
@@ -135,7 +133,7 @@ private:
     void decodeMidiEvent();
     dword_t readVarLen();
 
-    string readTextEvent();
+    std::string readTextEvent();
     dword_t readDataEvent(int expectedLength);
     void readMetaEvent(byte_t type);
     void ignoreSysexEvent(byte_t data);
@@ -156,10 +154,10 @@ private:
         }
     }
 
-    fstream& m_file;
+    std::fstream& m_file;
     int m_trackNumber;
 
-    streampos m_filePos;
+    std::streampos m_filePos;
     dword_t m_trackLength;
     dword_t m_trackLengthCounter;
     CQueue<CMidiEvent>* m_trackEventQueue;

src/Song.cpp

@@ -56,7 +56,7 @@ void CSong::loadSong(const QString & filename)
      fn = fn.replace('/','\\');
 #endif
     m_midiFile->setLogLevel(3);
-    m_midiFile->openMidiFile(string(fn.toLocal8Bit().data()));
+    m_midiFile->openMidiFile(std::string(fn.toLocal8Bit().data()));
     ppLogInfo("Opening song %s",  fn.toLocal8Bit().data());
     transpose(0);
     midiFileInfo();
@@ -266,7 +266,7 @@ bool CSong::pcKeyPress(int key, bool down)
         return true;
     }
 
-    for (j = 0; j < arraySize(pcNoteLookup); j++)
+    for (j = 0; j < arraySizeAs<std::size_t>(pcNoteLookup); j++)
     {
         if ( key==pcNoteLookup[j].key)
         {

src/Util.h

@@ -36,8 +36,6 @@
 #include <QString>
 #include <QApplication>
 
-using namespace std;
-
 #define MAX_MIDI_CHANNELS       16      // There are always at most 16 midi channels
 #define MIDDLE_C                60
 #define MIDI_OCTAVE             12