libcurl needlessly linked in for proxy, brings in additional 16 libs

zabbix proxy automatically compiles with libcurl support... even though it is unused at this time.
to make things worse, on a test system that results in 24 files being linked in for zabbix proxy. just disabling libcurl brings that count down to 8.(libcurl pulls in the additional ones...).

size wise, proxy binary is ~32KB bigger as a result.

libcurl simply should not be included by default, neither for server, nor for proxy.