Revert "use 'add()' rather than 'push_back()' API (so options are respected)"
Revert "use 'add()' rather than 'push_back()' API (so options are respected)"

This reverts commit 20eff097b7f97b6ba0a196747331a3c3d49f286a.

JanMarvin/rstudio,jrnold/rstudio,JanMarvin/rstudio,jrnold/rstudio,jar1karp/rstudio,jar1karp/rstudio,jar1karp/rstudio,JanMarvin/rstudio,jrnold/rstudio,jrnold/rstudio,jrnold/rstudio,jar1karp/rstudio,jar1karp/rstudio,jrnold/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,jar1karp/rstudio,jar1karp/rstudio,jrnold/rstudio,jrnold/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,jar1karp/rstudio,jrnold/rstudio,jar1karp/rstudio,JanMarvin/rstudio