Proposal: Add support to runConfigureICU for Linux IA64 Intel ECC compiler

To the usage() function, add the following option:

    IA64/LINUX/ECC          Use the Intel 70 ECC compiler on IA64 Linux

To case $platform in statement, add the following block:

    IA64/LINUX/ECC)
        THE_OS="Linux"
        THE_COMP="Intel ECC 70"
        CC=ecc; export CC
        CXX=ecpc; export CXX
        ;;

Any objections?