Make comments more consistent

- Changes most `/* comments */` to `// comments`
- Changes `/**` block comments consistently to `/*`
- Adds consistent license comments to all files

Also renames `T_POP_SET` to `T_Z80_SET`

include/link/object.h

@@ -6,37 +6,37 @@
  * SPDX-License-Identifier: MIT
  */
 
-/* Declarations related to processing of object (.o) files */
+// Declarations related to processing of object (.o) files
 
 #ifndef RGBDS_LINK_OBJECT_H
 #define RGBDS_LINK_OBJECT_H
 
-/**
+/*
  * Read an object (.o) file, and add its info to the data structures.
  * @param fileName A path to the object file to be read
  * @param i The ID of the file
  */
 void obj_ReadFile(char const *fileName, unsigned int i);
 
-/**
+/*
  * Perform validation on the object files' contents
  */
 void obj_DoSanityChecks(void);
 
-/**
+/*
  * Evaluate all assertions
  */
 void obj_CheckAssertions(void);
 
-/**
+/*
  * Sets up object file reading
  * @param nbFiles The number of object files that will be read
  */
 void obj_Setup(unsigned int nbFiles);
 
-/**
+/*
  * `free`s all object memory that was allocated.
  */
 void obj_Cleanup(void);
 
-#endif /* RGBDS_LINK_OBJECT_H */
+#endif // RGBDS_LINK_OBJECT_H