[Memory/CPU] UWP: Support separate code execution and write memory, FromApp functions + other Windows memory fixes

src/xenia/base/memory.h

@@ -35,6 +35,7 @@ enum class PageAccess {
   kNoAccess = 0,
   kReadOnly = 1 << 0,
   kReadWrite = kReadOnly | 1 << 1,
+  kExecuteReadOnly = kReadOnly | 1 << 2,
   kExecuteReadWrite = kReadWrite | 1 << 2,
 };
 
@@ -49,6 +50,16 @@ enum class DeallocationType {
   kDecommit = 1 << 1,
 };
 
+// Whether the host allows the pages to be allocated or mapped with
+// PageAccess::kExecuteReadWrite - if not, separate mappings backed by the same
+// memory-mapped file must be used to write to executable pages.
+bool IsWritableExecutableMemorySupported();
+
+// Whether PageAccess::kExecuteReadWrite is a supported and preferred way of
+// writing executable memory, useful for simulating how Xenia would work without
+// writable executable memory on a system with it.
+bool IsWritableExecutableMemoryPreferred();
+
 // Allocates a block of memory at the given page-aligned base address.
 // Fails if the memory is not available.
 // Specify nullptr for base_address to leave it up to the system.