Add unit-aware conversion of pressure data

This just adds (and uses) a string_to_pressure() to parse pressure units
correctly when filling in cylinder pressures.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

dive.h

@@ -818,6 +818,7 @@ extern double strtod_flags(const char *str, const char **ptr, unsigned int flags
 
 extern weight_t string_to_weight(const char *str);
 extern depth_t string_to_depth(const char *str);
+extern pressure_t string_to_pressure(const char *str);
 
 #include "pref.h"