edje_embryo: add printf feature.

edje_embryo: add printf feature.

Summary:
The edc debugging is difficult because users can not check
whether or not any program is executed or the state of part.
If users can print that property, they can do debugging more easily.
This "printf" feature is for debugging edc.

@feature

Test Plan:
add printf("test : %s %d %f", "text", 1, 0.5); in the script in the edc
build it by edje_cc
excute it and see the log

Reviewers: cedric, raster, jpeg

Reviewed By: jpeg

Subscribers: jpeg

Differential Revision: https://phab.enlightenment.org/D3499

Change-Id: Iaaed860a25e3b0fc0f2cce20a93dd238e4a0f41b