Fix jack client naming and improve use of pa_jack (#1847)

* Switch around Pa_Initialize and PaJack_SetClientName so that the jack
  client is named "Olive" on the first initialization and not on
  subsequent initializations when refreshing devices.
* Make use of pa_jack.h dependant on availability of the header and not
  on the usage of the linux platform.

Signed-off-by: Alfred Wingate <parona@protonmail.com>

app/audio/audiomanager.cpp

@@ -20,7 +20,7 @@
 
 #include "audiomanager.h"
 
-#ifdef Q_OS_LINUX
+#ifdef PA_HAS_JACK
 #include <pa_jack.h>
 #endif
 
@@ -202,14 +202,14 @@ PaDeviceIndex AudioManager::FindDeviceByName(const QString &s, bool is_output_de
 AudioManager::AudioManager() :
   output_stream_(nullptr)
 {
-  Pa_Initialize();
-
-#ifdef Q_OS_LINUX
+#ifdef PA_HAS_JACK
   // PortAudio doesn't do a strcpy, so we need a const char that's readily accessible (i.e. not
   // a QString converted to UTF-8)
   PaJack_SetClientName("Olive");
 #endif
 
+  Pa_Initialize();
+
   // Get device from config
   PaDeviceIndex output_device = FindConfigDeviceByName(true);
   PaDeviceIndex input_device = FindConfigDeviceByName(false);