cleanup: move FRACTION macro from dive.h to units.h

There appears to be no reason to slurp in all dive.h when compiling
membuffer.c. units.h might not seem like the perfect place, but it
is the most fitting I found.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/dive.h

@@ -396,8 +396,6 @@ extern const char *existing_filename;
 extern void subsurface_command_line_init(int *, char ***);
 extern void subsurface_command_line_exit(int *, char ***);
 
-#define FRACTION(n, x) ((unsigned)(n) / (x)), ((unsigned)(n) % (x))
-
 extern bool is_dc_planner(const struct divecomputer *dc);
 extern bool has_planned(const struct dive *dive, bool planned);
 

core/membuffer.c

@@ -9,7 +9,7 @@
 #include <string.h>
 #include <stdio.h>
 
-#include "dive.h"
+#include "units.h"
 #include "membuffer.h"
 
 /* Only for internal use */

core/units.h

@@ -13,6 +13,8 @@ extern "C" {
 #include <stdbool.h>
 #endif
 
+#define FRACTION(n, x) ((unsigned)(n) / (x)), ((unsigned)(n) % (x))
+
 #define O2_IN_AIR 209 // permille
 #define N2_IN_AIR 781
 #define O2_DENSITY 1331 // mg/Liter