Merge branch '63-boost-build-1-70-0-with-gcc-7-4-0-openmpi-3-1-4' into 'master'

Resolve "boost: build 1.70.0 with gcc/7.4.0 openmpi/3.1.4"

Closes #63

See merge request Pmodules/buildblocks!77

MPI/boost/files/variants.rhel6

@@ -9,10 +9,10 @@ boost/1.68.0-1       stable	gcc/7.3.0 openmpi/3.1.3 b:zlib/1.2.11
 
 boost/1.68.0         stable	gcc/8.2.0 openmpi/1.10.7 b:Python/2.7.14
 boost/1.68.0         stable	gcc/8.2.0 openmpi/2.1.5 b:Python/2.7.14
-boost/1.68.0         stable	gcc/8.2.0 openmpi/3.0.0 b:Python/2.7.14
 boost/1.68.0         stable	gcc/8.2.0 openmpi/3.1.2 b:Python/2.7.14
 boost/1.68.0         stable	gcc/8.2.0 openmpi/3.1.3 b:Python/2.7.14
 
 boost/1.68.0-1       stable	gcc/7.3.0 mpich/3.3 b:zlib/1.2.11
 
 boost/1.70.0         stable	gcc/7.3.0 openmpi/3.1.3 b:zlib/1.2.11
+boost/1.70.0         stable	gcc/7.4.0 openmpi/3.1.4 b:zlib/1.2.11