Reverse dependencies for gmp

Latest version of the following gems require gmp

Gem	Version	Date	Downloads
ruby-mpfr +55.7 Thousand Downloads	`0.0.17` November 05, 2013	November 05, 2013	55.7 Thousand
base58_gmp +37.9 Thousand Downloads	`1.0.0` September 28, 2016	September 28, 2016	37.9 Thousand
gnu_mpc +14.7 Thousand Downloads	`0.9.0` December 23, 2013	December 23, 2013	14.7 Thousand
gmp_ecm +8.22 Thousand Downloads	`0.3.1` November 12, 2012	November 12, 2012	8.22 Thousand