Loaders: Add cancelation to all file loaders.

Mainly, for HTTP which might be stalled trying to connect (especially if
you're not near your PC right now and it's in your recent, for example.)

Core/FileLoaders/RamCachingFileLoader.cpp

@@ -28,7 +28,7 @@
 
 // Takes ownership of backend.
 RamCachingFileLoader::RamCachingFileLoader(FileLoader *backend)
-	: filesize_(0), backend_(backend), exists_(-1), isDirectory_(-1), aheadThread_(false) {
+	: backend_(backend) {
 	filesize_ = backend->FileSize();
 	if (filesize_ > 0) {
 		InitCache();
@@ -107,11 +107,7 @@ void RamCachingFileLoader::InitCache() {
 }
 
 void RamCachingFileLoader::ShutdownCache() {
-	{
-		std::lock_guard<std::mutex> guard(blocksMutex_);
-		// Try to have the thread stop.
-		aheadRemaining_ = 0;
-	}
+	Cancel();
 
 	// We can't delete while the thread is running, so have to wait.
 	// This should only happen from the menu.
@@ -127,6 +123,15 @@ void RamCachingFileLoader::ShutdownCache() {
 	}
 }
 
+void RamCachingFileLoader::Cancel() {
+	if (aheadThread_) {
+		std::lock_guard<std::mutex> guard(blocksMutex_);
+		aheadCancel_ = true;
+	}
+
+	backend_->Cancel();
+}
+
 size_t RamCachingFileLoader::ReadFromCache(s64 pos, size_t bytes, void *data) {
 	s64 cacheStartPos = pos >> BLOCK_SHIFT;
 	s64 cacheEndPos = (pos + bytes - 1) >> BLOCK_SHIFT;
@@ -220,10 +225,11 @@ void RamCachingFileLoader::StartReadAhead(s64 pos) {
 	}
 
 	aheadThread_ = true;
+	aheadCancel_ = false;
 	std::thread th([this] {
 		setCurrentThreadName("FileLoaderReadAhead");
 
-		while (aheadRemaining_ != 0) {
+		while (aheadRemaining_ != 0 && !aheadCancel_) {
 			// Where should we look?
 			const u32 cacheStartPos = NextAheadBlock();
 			if (cacheStartPos == 0xFFFFFFFF) {