Add support for XAudio2 redistributable

Bundle XAudio2 to better support Win7

Fix wangqr/Aegisub#59

CMakeLists.txt

@@ -569,6 +569,13 @@ if(WIN32)
     if(WITH_XAUDIO2)
         target_compile_definitions(Aegisub PRIVATE "WITH_XAUDIO2")
         target_sources(Aegisub PRIVATE src/audio_player_xaudio2.cpp)
+        option(XAUDIO2_REDIST "Use XAudio redistributable")
+        if(XAUDIO2_REDIST)
+            find_package(XAudio2redist REQUIRED)
+            target_compile_definitions(Aegisub PRIVATE "XAUDIO2_REDIST")
+            target_include_directories(Aegisub PRIVATE ${XAudio2redist_INCLUDE_DIRS})
+            target_link_libraries(Aegisub PRIVATE ${XAudio2redist_LIBRARIES})
+        endif()
     endif()
 else()
     set(WITH_DIRECTSOUND OFF)

cmake/FindXAudio2redist.cmake

@@ -0,0 +1,13 @@
+find_path(XAudio2redist_INCLUDE_DIRS
+  NAMES xaudio2redist.h
+)
+find_library(XAudio2redist_LIBRARIES
+  NAMES xaudio2_9redist
+)
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(XAudio2redist
+  FOUND_VAR XAudio2redist_FOUND
+  REQUIRED_VARS
+    XAudio2redist_LIBRARIES
+    XAudio2redist_INCLUDE_DIRS
+)

src/audio_player_xaudio2.cpp

@@ -37,7 +37,11 @@
 #include <libaegisub/log.h>
 #include <libaegisub/make_unique.h>
 
+#ifndef XAUDIO2_REDIST
 #include <xaudio2.h>
+#else
+#include <xaudio2redist.h>
+#endif
 
 namespace {
 class XAudio2Thread;