CCR code: Split profile.c into two files, with gas caluclations separate.

This patch implements a separation of the code for gas pressure
calculations from the rest of the code in profile.c. The latter
file is now split into: profile.c and gaspressures.c. The
details of the transferred functions is given at the top of
gaspressures.c. The following chnages were made:
1) dive.h: The function types of calculate_depth_to_mbar
   and depth_to_mbar were made non-static in order to make them
   available within gaspressures.c.
2) profile.c: Prototypes for the functions in gaspressures.c
   were inserted at the top of profile. Ten functions were
   transferred from profile.c to gaspressures.c
3) gaspressures.c as well as a short header, gaspressures.h
   were created.

For the gas pressure calculations for CCR dives, gaspressures.c
forms the immediate basis for further code development.

Signed-off-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

subsurface.pro

@@ -38,6 +38,7 @@ HEADERS = \
 	worldmap-options.h \
 	pref.h \
 	profile.h \
+	gaspressures.h \
 	qt-gui.h \
 	qthelper.h \
 	units.h \
@@ -117,6 +118,7 @@ SOURCES =  \
 	parse-xml.c \
 	planner.c \
 	profile.c \
+	gaspressures.c \
 	divecomputer.cpp \
 	worldmap-save.c \
 	save-html.c \