tree data new BUGFIX correctly mark lyd_new_term_bin definition

[gotthardp]

The lyd_new_term_bin is declared as an API function using LIBYANG_API_DECL.
Its definition however also uses LIBYANG_API_DECL, whereas I believe it should use LIBYANG_API_DEF like all the other functions.

/** Exporting symbols to a shared library and importing back afterwards
 *
 * - use LIBYANG_API_DECL to mark a declaration in the public header
 * - use LIBYANG_API_DEF to mark a definition (in the source code for the actual implementaiton)
 * */

[michalvasko]

Right, thanks.