Refactor FourCC magic uses

- Use new fourcc_t type
- Improves compiler compatibility by removing multi chars

src/xenia/cpu/processor.cc

@@ -432,12 +432,12 @@ void Processor::LowerIrql(Irql old_value) {
 }
 
 bool Processor::Save(ByteStream* stream) {
-  stream->Write('PROC');
+  stream->Write(kProcessorSaveSignature);
   return true;
 }
 
 bool Processor::Restore(ByteStream* stream) {
-  if (stream->Read<uint32_t>() != 'PROC') {
+  if (stream->Read<uint32_t>() != kProcessorSaveSignature) {
     XELOGE("Processor::Restore - Invalid magic value!");
     return false;
   }

src/xenia/cpu/processor.h

@@ -34,6 +34,8 @@ DECLARE_bool(debug);
 namespace xe {
 namespace cpu {
 
+constexpr fourcc_t kProcessorSaveSignature = make_fourcc("PROC");
+
 class Breakpoint;
 class StackWalker;
 class XexModule;

src/xenia/cpu/xex_module.cc

@@ -899,9 +899,9 @@ bool XexModule::Load(const std::string_view name, const std::string_view path,
                      const void* xex_addr, size_t xex_length) {
   auto src_header = reinterpret_cast<const xex2_header*>(xex_addr);
 
-  if (src_header->magic == 'XEX1') {
+  if (src_header->magic == kXEX1Signature) {
     xex_format_ = kFormatXex1;
-  } else if (src_header->magic == 'XEX2') {
+  } else if (src_header->magic == kXEX2Signature) {
     xex_format_ = kFormatXex2;
   } else {
     return false;

src/xenia/cpu/xex_module.h

@@ -25,6 +25,10 @@ class KernelState;
 namespace xe {
 namespace cpu {
 
+constexpr fourcc_t kXEX1Signature = make_fourcc("XEX1");
+constexpr fourcc_t kXEX2Signature = make_fourcc("XEX2");
+constexpr fourcc_t kElfSignature = make_fourcc(0x7F, 'E', 'L', 'F');
+
 class Runtime;
 
 class XexModule : public xe::cpu::Module {