make: multiple definition of `base64` and `unbase64`

[zypA13510]

/usr/bin/ld: ot_http.o: in function `base64':
ot_http.c:(.text+0x200): multiple definition of `base64'; ot_udp.o:ot_udp.c:(.text+0x0): first defined here
/usr/bin/ld: ot_http.o: in function `unbase64':
ot_http.c:(.text+0x420): multiple definition of `unbase64'; ot_udp.o:ot_udp.c:(.text+0x220): first defined here
collect2: error: ld returned 1 exit status
make: *** [Makefile:80: opentracker] Error 1

[m6n50u7]

I fixed the error by changing the functions' names and making them static.