glue 1.7.0

• If rlang is installed, glue will generate more informative errors if an
  interpolated expression either can't be parsed or fails to evaluate (#229).

• + now works in more situations, and gives errors when one side isn't a
  character vector. It no longer automatically applies glue interpolation to
  a non-glue input, if there is one. You'll need to do that yourself (#286).

• glue_collapse(character()) (and hence glue_sql_collapse(character())) now
  return "", so that they always return a single string (#88).

• glue_sql() now collapses an empty vector to "" not "NULL" (#272).

• glue_sql() now uses DBI::dbQuoteLiteral() for all object types. This
  should increase fidelity of escaping for different object types (#279).

• The "Speed of glue" vignette has been converted to an article, which allows
  several package to be removed from Suggests (and re-located to
  Config/Needs/website). The code got a light refresh, including a switch
  from microbenchmark to bench and more modern use of ggplot2.

• Add $(C_VISIBILITY) to compiler flags to hide internal symbols from the dll (#284 @lionel-).