common.h: general clean up

Remove unused functions and definitions. Move some macros into the files
they belong.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/atom.c

@@ -4,9 +4,6 @@
 #include "common.h"
 #include "utils.h"
 
-/**
- * Wrapper of XInternAtom() for convenience.
- */
 static inline void *atom_getter(void *ud, const char *atom_name, int *err) {
 	xcb_connection_t *c = ud;
 	xcb_intern_atom_reply_t *reply = xcb_intern_atom_reply(
@@ -25,7 +22,7 @@ static inline void *atom_getter(void *ud, const char *atom_name, int *err) {
 }
 
 /**
- * Fetch all required atoms and save them to a session.
+ * Create a new atom structure and fetch all predefined atoms
  */
 struct atom *init_atoms(xcb_connection_t *c) {
 	auto atoms = ccalloc(1, struct atom);