fixed "unknown pragma" warnings for GCC

lib-src/header-substitutes/allegro.h

@@ -2,7 +2,16 @@
 // Indirectly include Allegro header so that we can disable warnings about unused parameters
 // when compiling Audacity itself.
 
+#ifdef _MSC_VER
+// If this is compiled with MSVC (Visual Studio)
+
 #pragma warning( push )
 #pragma warning( disable : 4100)
 #include "../portsmf/allegro.h"
-#pragma warning( pop ) 
+#pragma warning( pop )
+
+#else //_MSC_VER
+
+#include "../portsmf/allegro.h"
+
+#endif //_MSC_VER

lib-src/header-substitutes/sbsms.h

@@ -2,7 +2,15 @@
 // Indirectly include SBSMS header so that we can disable warnings about unused parameters
 // when compiling Audacity itself.
 
+#ifdef _MSC_VER
+// If this is compiled with MSVC (Visual Studio)
 #pragma warning( push )
 #pragma warning( disable : 4100)
 #include "../sbsms/include/sbsms.h"
-#pragma warning( pop ) 
+#pragma warning( pop )
+
+#else //_MSC_VER
+
+#include "../sbsms/include/sbsms.h"
+
+#endif //_MSC_VER

src/AudacityApp.cpp

@@ -1064,8 +1064,11 @@ void AudacityApp::OnFatalException()
 }
 
 
+#ifdef _MSC_VER
+// If this is compiled with MSVC (Visual Studio)
 #pragma warning( push )
 #pragma warning( disable : 4702) // unreachable code warning.
+#endif //_MSC_VER
 
 bool AudacityApp::OnExceptionInMainLoop()
 {
@@ -1109,7 +1112,9 @@ bool AudacityApp::OnExceptionInMainLoop()
    // Shouldn't ever reach this line
    return false;
 }
+#ifdef _MSC_VER
 #pragma warning( pop )
+#endif //_MSC_VER
 
 #if defined(EXPERIMENTAL_CRASH_REPORT)
 void AudacityApp::GenerateCrashReport(wxDebugReport::Context ctx)