Avoid using type 'gasmix_t': use 'struct gasmix' instead

libdivecomputer already uses 'gasmix_t' for its own gasmix thing.  I
don't like th eway we step on each others name spaces, but hey, might as
well just use 'struct gasmix' and avoid the typedef.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

dive.h

@@ -69,10 +69,10 @@ typedef struct {
 	int grams;
 } weight_t;
 
-typedef struct {
+struct gasmix {
 	fraction_t o2;
 	fraction_t he;
-} gasmix_t;
+};
 
 typedef struct {
 	volume_t size;
@@ -82,7 +82,7 @@ typedef struct {
 
 typedef struct {
 	cylinder_type_t type;
-	gasmix_t gasmix;
+	struct gasmix gasmix;
 	pressure_t start, end;
 } cylinder_t;