After installing gcc and required devel packages from perzl.org and issuing the following:
./configure --prefix=/opt/zabbix3 --enable-server --enable-agent --with-ibm-db2=/home/db2inst1/sqllib --enable-ipv6 --with-net-snmp --with-libcurl --with-libxml2

Make stops in zbxmedia:

Making all in zbxmedia
gcc -DHAVE_CONFIG_H -I. -I../../../include -g -O2 -I/home/db2inst1/sqllib/include -I/opt/freeware/include/libxml2 -I/opt/freeware/include -I. -I/opt/freeware/include -MT email.o -MD -MP -MF .deps/email.Tpo -c -o email.o email.c
mv -f .deps/email.Tpo .deps/email.Po
gcc -DHAVE_CONFIG_H -I. -I../../../include -g -O2 -I/home/db2inst1/sqllib/include -I/opt/freeware/include/libxml2 -I/opt/freeware/include -I. -I/opt/freeware/include -MT eztexting.o -MD -MP -MF .deps/eztexting.Tpo -c -o eztexting.o eztexting.c
mv -f .deps/eztexting.Tpo .deps/eztexting.Po
gcc -DHAVE_CONFIG_H -I. -I../../../include -g -O2 -I/home/db2inst1/sqllib/include -I/opt/freeware/include/libxml2 -I/opt/freeware/include -I. -I/opt/freeware/include -MT sms.o -MD -MP -MF .deps/sms.Tpo -c -o sms.o sms.c
sms.c: In function 'send_sms':
sms.c:257:42: error: 'CRTSCTS' undeclared (first use in this function)
options.c_cflag = old_options.c_cflag | CRTSCTS | CS8 | CLOCAL | CREAD;
^
sms.c:257:42: note: each undeclared identifier is reported only once for each function it appears in
make: 1254-004 The error code from the last command is 1.

Stop.
make: 1254-004 The error code from the last command is 1.

Stop.
make: 1254-004 The error code from the last command is 1.

Stop.
make: 1254-004 The error code from the last command is 1.

Stop.

As a workaround, I removed CRTSCTS and was able to compile:

*** src/libs/zbxmedia/sms.c.dist        Wed Sep  9 10:07:13 2015
--- src/libs/zbxmedia/sms.c     Mon Sep 14 11:24:27 2015
***************
*** 254,260 ****
  #ifdef ONOCR
        options.c_oflag = ONOCR;
  #endif
!       options.c_cflag = old_options.c_cflag | CRTSCTS | CS8 | CLOCAL | CREAD;
        options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
        options.c_cc[VMIN] = 0;
        options.c_cc[VTIME] = 1;
--- 254,260 ----
  #ifdef ONOCR
        options.c_oflag = ONOCR;
  #endif
!       options.c_cflag = old_options.c_cflag | CS8 | CLOCAL | CREAD;
        options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
        options.c_cc[VMIN] = 0;
        options.c_cc[VTIME] = 1;