Summary:
Add eina_tmpstr_manage_new, eina_tmpstr_manage_new_length APIs, these APIs create new tmpstr but reuse the input string memory.
@feature
Test Plan: Test case and example updated
Reviewers: tasn, cedric
Reviewed By: cedric
Differential Revision: https://phab.enlightenment.org/D3178
Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>