Update {virtual,override} to follow C++11 style in courgette.

courgette/disassembler_elf_32_x86.h

Index: courgette/disassembler_elf_32_x86.h
diff --git a/courgette/disassembler_elf_32_x86.h b/courgette/disassembler_elf_32_x86.h
index bc83a04c4c863f2f2179b914fe90daf937c5f097..913e93f98c7f44924c8eedfc55090d29b5222eb4 100644
--- a/courgette/disassembler_elf_32_x86.h
+++ b/courgette/disassembler_elf_32_x86.h
@@ -21,17 +21,17 @@ class DisassemblerElf32X86 : public DisassemblerElf32 {
     explicit TypedRVAX86(RVA rva) : TypedRVA(rva) {
     }
 
-    virtual CheckBool ComputeRelativeTarget(const uint8* op_pointer) override {
+    CheckBool ComputeRelativeTarget(const uint8* op_pointer) override {
       set_relative_target(Read32LittleEndian(op_pointer) + 4);
       return true;
     }
 
-    virtual CheckBool EmitInstruction(AssemblyProgram* program,
-                                       RVA target_rva) override {
+    CheckBool EmitInstruction(AssemblyProgram* program,
+                              RVA target_rva) override {
       return program->EmitRel32(program->FindOrMakeRel32Label(target_rva));
     }
 
-    virtual uint16 op_size() const override { return 4; }
+    uint16 op_size() const override { return 4; }
   };
 
   explicit DisassemblerElf32X86(const void* start, size_t length);