Update mpfr version to 3.1.6

This updates the mpfr version to 3.1.6 which is the last bugfix
release from the 3.1.x series and avoids printing the version
is buggy but acceptable from our configury.

2021-05-17  Richard Biener  <rguenther@suse.de>

contrib/ChangeLog:
	* download_prerequisites: Update mpfr version to 3.1.6.
	* prerequisites.md5: Update.
	* prerequisites.sha512: Likewise.

contrib/download_prerequisites

@@ -28,7 +28,7 @@ version='(unversioned)'
 # `contrib/prerequisites.md5` with the new checksums.
 
 gmp='gmp-6.1.0.tar.bz2'
-mpfr='mpfr-3.1.4.tar.bz2'
+mpfr='mpfr-3.1.6.tar.bz2'
 mpc='mpc-1.0.3.tar.gz'
 isl='isl-0.18.tar.bz2'
 

contrib/prerequisites.md5

 86ee6e54ebfc4a90b643a65e402c4048  gmp-6.1.0.tar.bz2
-b8a2f6b0e68bef46e53da2ac439e1cf4  mpfr-3.1.4.tar.bz2
+320c28198def956aeacdb240b46b8969  mpfr-3.1.6.tar.bz2
 d6a1d5f8ddea3abd2cc3e98f58352d26  mpc-1.0.3.tar.gz
 11436d6b205e516635b666090b94ab32  isl-0.18.tar.bz2

contrib/prerequisites.sha512

 3c82aeab9c1596d4da8afac2eec38e429e84f3211e1a572cf8fd2b546493c44c039b922a1133eaaa48bd7f3e11dbe795a384e21ed95cbe3ecc58d7ac02246117  gmp-6.1.0.tar.bz2
-51066066ff2c12ed2198605ecf68846b0c96b548adafa5b80e0c786d0df488411a5e8973358fce7192dc977ad4e68414cf14500e3c39746de62465eb145bb819  mpfr-3.1.4.tar.bz2
+0c310dd7956be527884f8059c195a5aca1042b089d0927ac6341e6310b1250a7059bc61aaaab4dfb76c6ab8b67e440878ca203f72674529bbcb46770ed9b6885  mpfr-3.1.6.tar.bz2
 0028b76df130720c1fad7de937a0d041224806ce5ef76589f19c7b49d956071a683e2f20d154c192a231e69756b19e48208f2889b0c13950ceb7b3cfaf059a43  mpc-1.0.3.tar.gz
 85d0b40f4dbf14cb99d17aa07048cdcab2dc3eb527d2fbb1e84c41b2de5f351025370e57448b63b2b8a8cf8a0843a089c3263f9baee1542d5c2e1cb37ed39d94  isl-0.18.tar.bz2