Initial working version androidhelper.c

On android, Qt libraries are not to be used. But there are some important
functions implemented in qthelper.cpp which will be needed for subsurface
library on android. Hence, as a replacement, androidhelper.c will provide all
those functions. Exif related functions are not implemented yet as it would need
cpp. Instead, I think libexif should be used.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>
Implemented picture_load_exif_data using libexif

Earlier, exif.cpp was being used but the implementation being in c, the function
is now implemented using libexif library. This function loads latitude,
longitude and timestamp present in a picture. Absence of these should set the
values to zero.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>
Add replacement of divecomputer.cpp for android

Removing all the qt parts and implementing those in C. This is done specially
for android. It is untested and needs thorough testing.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>
Building core libraries on android

Subsurface on android needs to use all the core features of subsurface. To cross
compile them for android using ndk-build, Android.mk file is needed. This also
includes some custom files made for android like androidhelper.c/h
divecomputer_android.c/h
This mk file should be referred by android applications using NDK_MODULE_PATH
and $(call import-module, subsurface)

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>
Empty gettext.c for android

Translations on android should be taken care of by this file. But presently, it
is empty and would return the same string passed to it.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>