Resolve timestamp name conflict.

[pawel-soja]

The INDI and GPSD projects declare a timestamp function with different behavior and return types.
The suggestion is to rename the function in the INDI Core library from timestamp to indi_timestamp. This is a function also available in C, so the namespace is omitted.

The problem appeared when compiling indi-3rdparty on Raspberry PI.

[ 71%] Building CXX object indi-armadillo-platypus/CMakeFiles/indi_seletek_rotator.dir/seletek_rotator.cpp.o
In file included from /usr/include/libgpsmm.h:12,
                 from /home/pi/Projects/indi-3rdparty/indi-gpsd/gps_driver.cpp:31:
/usr/include/gps.h:2106:20: error: conflicting declaration of C function ‘timestamp_t timestamp()’
 extern timestamp_t timestamp(void);
                    ^~~~~~~~~
In file included from /usr/include/libindi/indidriver.h:28,
                 from /usr/include/libindi/defaultdevice.h:22,
                 from /usr/include/libindi/indigps.h:27,
                 from /home/pi/Projects/indi-3rdparty/indi-gpsd/gps_driver.h:28,
                 from /home/pi/Projects/indi-3rdparty/indi-gpsd/gps_driver.cpp:26:
/usr/include/libindi/indicom.h:349:13: note: previous declaration ‘const char* timestamp()’
 const char *timestamp();

[pawel-soja]

I didn't expect the feature to be so popular.
In kstars you need to make a fix and change timestamp() to indi_timestamp()

[knro]

Yes it's already done!