gb-emu: initial commit

Add a mostly non-functional Gameboy CPU and the skeleton
of a Gameboy assembler intended for unit tests.

src/tests/gbasm/test.h

@@ -0,0 +1,19 @@
+#ifndef GBASM_TEST_H
+#define GBASM_TEST_H
+
+#include <stdint.h>
+
+struct gbasm_test {
+	const char *name;
+	const char *asm_source;
+	const uint8_t *expected_output;
+	const int expected_output_len;
+};
+
+struct gbasm_tests {
+	const char *name;
+	int num_tests;
+	const struct gbasm_test **tests;
+};
+
+#endif