fix compilation warnings on Niagara clusters

[pachadotdev]

Hi Davis

I hope you are doing well.

I am using cpp11 with vendoring to run my codes in the Niagara clusters. When I run my codes there, I get these warnings

── R CMD INSTALL ───────────────────────────────────────────────────────────────
─  installing *source* package ‘blazebenchmark’ ... (386ms)
   ** using staged installation
   ** libs
   g++ -std=gnu++14 -I"/scinet/niagara/software/2019b/opt/gcc-8.3.0/r/4.2.2-batteries-included/lib64/R/include" -DNDEBUG   -I/usr/local/include   -DARMA_OPENMP_THREADS=40 -I../inst/include -fpic  -O2 -ftree-vectorize -march=native  -UNDEBUG -Wall -pedantic -g -O0 -fdiagnostics-color=always -c 01_own_functions.cpp -o 

   ../inst/include/cpp11/r_vector.hpp:425:2: warning: extra ‘;’ [-Wpedantic]
   ../inst/include/cpp11/r_vector.hpp:451:2: warning: extra ‘;’ [-Wpedantic]
   ../inst/include/cpp11/list.hpp:57:2: warning: extra ‘;’ [-Wpedantic]
   ../inst/include/cpp11/doubles.hpp:53:2: warning: extra ‘;’ [-Wpedantic]
   ../inst/include/cpp11/integers.hpp:54:2: warning: extra ‘;’ [-Wpedantic]
   ../inst/include/cpp11/logicals.hpp:53:2: warning: extra ‘;’ [-Wpedantic]
   ../inst/include/cpp11/raws.hpp:61:2: warning: extra ‘;’ [-Wpedantic]
   ../inst/include/cpp11/strings.hpp:54:2: warning: extra ‘;’ [-Wpedantic]

This PR solves that and it works exactly the same with with a cleaner log.

Best,

[DavisVaughan]

Thanks!