CI/travis/lib.sh: add echo_[red,green,blue] functions
CI/travis/lib.sh: add echo_[red,green,blue] functions

These will be useful for marking out important messages in logs.

Signed-off-by: Alexandru Ardelean <685557f6b7c225d86b536740313ed51b24843a58@analog.com>

analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio