Refactor installer: differentiate software version

For clarity,the minimum_version bash variable, which holds the
version number for the package that will potentially be installed
no longer has the same name as the wrapped package in the case
of mpich wrapping gfortran.

Author: Damian Rouson

prerequisites/install-functions/find_or_install.sh

@@ -173,12 +173,12 @@ find_or_install()
 
         else
 
-          export minimum_version=$(./build.sh -V gcc)
-          info "$this_script: Checking whether $executable in PATH wraps gfortran version >= $minimum_version... "
+          export minimum_compiler_version=$(./build.sh -V gcc)
+          info "$this_script: Checking whether $executable in PATH wraps gfortran version >= $minimum_compiler_version... "
           $executable acceptable_compiler.f90 -o acceptable_compiler || true;
           $executable print_true.f90 -o print_true || true;
           if [[ -f ./acceptable_compiler && -f ./print_true ]]; then
-            acceptable=$(./acceptable_compiler $minimum_version)
+            acceptable=$(./acceptable_compiler $minimum_compiler_version)
             is_true=$(./print_true)
             rm acceptable_compiler print_true
           else