Removed setlocale instances https://github.com/oetiker/rrdtool-1.x/issues/504

This branch does the following:
1) Removes instances of setlocale
2) Added rrd_strtod function, which is a locale independent version of strtod function 
3) Made most of the code to use rrd_strtod & rrd_snprintf instead of strtod, atof & snprintf
If I do not make this change then I get this error during make: 

rrdcached-rrd_daemon.o: In function `handle_request_update':
/home/upasana/RRDTool/rrdtool-1.x/src/rrd_daemon.c:1515: undefined reference to `rrd_strtod'
collect2: error: ld returned 1 exit status
make[2]: *** [rrdcached] Error 1
make[2]: Leaving directory `/home/upasana/RRDTool/rrdtool-1.x/src'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/home/upasana/RRDTool/rrdtool-1.x/src'
make: *** [all-recursive] Error 1

I've included rrd_strtod.h in rrd_daemon, but no idea why it's giving me this error!