Make the PortAudio DLL a part of the FlexASIO DLL assembly.

Fixes #47.

src/flexasio/FlexASIO/CMakeLists.txt

@@ -67,7 +67,7 @@ target_link_libraries(FlexASIO_flexasio
 )
 
 # Note: this is SHARED, not MODULE, otherwise CMake refuses to link that in FlexASIOTest.
-add_library(FlexASIO SHARED dll.def flexasio.rc ../versioninfo.rc)
+add_library(FlexASIO SHARED dll.def flexasio.rc ../versioninfo.rc flexasio.manifest)
 target_compile_definitions(FlexASIO PRIVATE PROJECT_DESCRIPTION="FlexASIO ASIO Driver DLL")
 target_link_libraries(FlexASIO
 	PRIVATE FlexASIO_cflexasio

src/flexasio/FlexASIO/flexasio.manifest

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+  <!--
+    This ensures that, when FlexASIO.dll is loaded, the Windows DLL Loader loads the PortAudio DLL that ships with FlexASIO.
+    Otherwise, we can run into a subtle problem with some applications that also link with PortAudio directly;
+    indeed, in that case, the default behaviour of the Windows DLL Loader is to reuse the DLL that's already
+    loaded, which could be different from the one that FlexASIO expects. Unpredictable behaviour ensues.
+    See https://github.com/dechamps/FlexASIO/issues/47 for details.
+    
+    Note that we specify both 32-bit and 64-bit DLLs here. Only one of those actually exists, but the Windows
+    loader seems to be fine with ignoring non-existent files.
+  -->
+  <file name="portaudio_x64.dll" />
+  <file name="portaudio_x86.dll" />
+</assembly>