Removed usage of ASCII C strings in several places

Still QString::toAscii() & friends were used in several places causing
problems such as failed access to files with non-ASCII characters in
name.

Closes #2884115.
(cherry picked from commit 1633cf2593)

plugins/flp_import/FlpImport.cpp

@@ -1874,7 +1874,8 @@ extern "C"
 // neccessary for getting instance out of shared lib
 Plugin * PLUGIN_EXPORT lmms_plugin_main( Model *, void * _data )
 {
-	return new FlpImport( static_cast<const char *>( _data ) );
+	return new FlpImport( QString::fromUtf8(
+									static_cast<const char *>( _data ) ) );
 }
 
 }

plugins/midi_import/MidiImport.cpp

@@ -563,12 +563,10 @@ extern "C"
 // neccessary for getting instance out of shared lib
 Plugin * PLUGIN_EXPORT lmms_plugin_main( Model *, void * _data )
 {
-	return new MidiImport( static_cast<const char *>( _data ) );
+	return new MidiImport( QString::fromUtf8(
+									static_cast<const char *>( _data ) ) );
 }
 
 
 }
 
-
-#undef pos
-#undef setValue

plugins/patman/patman.cpp

@@ -210,7 +210,7 @@ patmanInstrument::LoadErrors patmanInstrument::loadPatch(
 {
 	unloadCurrentPatch();
 
-	FILE * fd = fopen( _filename.toAscii().constData() , "rb" );
+	FILE * fd = fopen( _filename.toUtf8().constData() , "rb" );
 	if( !fd )
 	{
 		perror( "fopen" );

src/gui/embed.cpp

@@ -79,10 +79,10 @@ QPixmap getIconPixmap( const char * _name, int _w, int _h )
 				p = QPixmap( 1, 1 );
 			}
 		}
-		return( p );
+		return p;
 	}
-	return( getIconPixmap( _name ).scaled( _w, _h, Qt::IgnoreAspectRatio,
-						Qt::SmoothTransformation ) );
+	return getIconPixmap( _name ).
+			scaled( _w, _h, Qt::IgnoreAspectRatio, Qt::SmoothTransformation );
 }
 
 
@@ -91,7 +91,7 @@ QPixmap getIconPixmap( const char * _name, int _w, int _h )
 QString getText( const char * _name )
 {
 	const embed::descriptor & e = findEmbeddedData( _name );
-	return( QString::fromLatin1( (const char *) e.data, e.size ) );
+	return QString::fromUtf8( (const char *) e.data, e.size );
 }