Add helper #defines to allow declaring embedded resources by name

* We want to be able to declare a 'name' of a resource and then fetch it
  later. To do this we create a tiny little reference (either an int on
  windows, or a pointer+length elsewhere), then actually fetch the data
  later.

renderdoc/os/posix/posix_specific.h

@@ -32,9 +32,19 @@
 
 #define OS_DEBUG_BREAK() raise(SIGTRAP)
 
-#define GetEmbeddedResource(filename) \
-  string(&CONCAT(data_, filename)[0], \
-         &CONCAT(data_, filename)[0] + CONCAT(CONCAT(data_, filename), _len))
+struct EmbeddedResourceType
+{
+  EmbeddedResourceType(const unsigned char *b, int l) : base(b), len(l) {}
+  const unsigned char *base;
+  int len;
+  std::string Get() const { return std::string(base, base + len); }
+};
+
+#define EmbeddedResource(filename) \
+  EmbeddedResourceType(&CONCAT(data_, filename)[0], CONCAT(CONCAT(data_, filename), _len))
+
+#define GetEmbeddedResource(filename) EmbeddedResource(filename).Get()
+#define GetDynamicEmbeddedResource(resource) resource.Get()
 
 namespace OSUtility
 {

renderdoc/os/win32/win32_specific.h

@@ -36,8 +36,11 @@
 
 #define OS_DEBUG_BREAK() __debugbreak()
 
-#define GetEmbeddedResource(filename) GetEmbeddedResourceWin32(CONCAT(RESOURCE_, filename))
-string GetEmbeddedResourceWin32(int resource);
+#define EmbeddedResourceType int
+#define EmbeddedResource(filename) CONCAT(RESOURCE_, filename)
+
+#define GetEmbeddedResource(filename) GetDynamicEmbeddedResource(EmbeddedResource(filename))
+std::string GetDynamicEmbeddedResource(int resource);
 
 namespace StringFormat
 {

renderdoc/os/win32/win32_stringio.cpp

@@ -41,7 +41,7 @@ using std::wstring;
 // gives us an address to identify this dll with
 static int dllLocator = 0;
 
-string GetEmbeddedResourceWin32(int resource)
+std::string GetDynamicEmbeddedResource(int resource)
 {
   HMODULE mod = NULL;
   GetModuleHandleExA(