Revert "remove gflib"

This reverts commit 8b59909ac5.

gflib/gpu_regs.h

@@ -0,0 +1,19 @@
+#ifndef GUARD_GPU_REGS_H
+#define GUARD_GPU_REGS_H
+
+// Exported type declarations
+
+// Exported RAM declarations
+
+// Exported ROM declarations
+void InitGpuRegManager(void);
+void CopyBufferedValuesToGpuRegs(void);
+void SetGpuReg(u8 regOffset, u16 value);
+void SetGpuReg_ForcedBlank(u8 regOffset, u16 value);
+u16 GetGpuReg(u8 regOffset);
+void SetGpuRegBits(u8 regOffset, u16 mask);
+void ClearGpuRegBits(u8 regOffset, u16 mask);
+void EnableInterrupts(u16 mask);
+void DisableInterrupts(u16 mask);
+
+#endif //GUARD_GPU_REGS_H