Update default GCC version to 6.1.0

In the absence of any arguments that override
the corresponding default behavior, ./install.sh
now builds GCC 6.1.0 if no GCC installation with
that version number or greater is in the PATH or
in prerequisites/installations.

This commit also adjusts related documentation,
screen output, and compiler acceptability checks.

Author: Damian Rouson

INSTALL.md

@@ -117,7 +117,7 @@ The prerequisites below and their dependencies are recommended for the broadest
 opencoarrays
 ├── cmake-3.4.0
 └── mpich-3.1.4
-    └── gcc-5.3.0
+    └── gcc-6.1.0
         ├── flex-2.6.0
         │   └── bison-3.0.4
         │       └── m4-1.4.17

doc/dependency_tree/opencoarrays-tree.txt

@@ -1,7 +1,7 @@
 opencoarrays
 ├── cmake-3.4.0
 └── mpich-3.1.4
-    └── gcc-5.3.0
+    └── gcc-6.1.0
         ├── flex-2.6.0
         │   └── bison-3.0.4
         │       └── m4-1.4.17

doc/dependency_tree/opencoarrays/mpich-3.1.4/gcc-5.1.0/flex-2.6.0/bison-3.0.4/m4-1.4.17/.gitkeep

@@ -35,5 +35,5 @@
 program main
   use iso_fortran_env, only : compiler_version
   implicit none
-  print *,compiler_version() >= "GCC version 5.3.0 "
+  print *,compiler_version() >= "GCC version 6.1.0 "
 end program

doc/dependency_tree/opencoarrays/mpich-3.1.4/gcc-5.1.0/gmp/.gitkeep

@@ -18,7 +18,7 @@ set_or_print_default_version()
   # See http://stackoverflow.com/questions/1494178/how-to-define-hash-tables-in-bash
   package_version=(
     "cmake:3.4.0"
-    "gcc:5.3.0"
+    "gcc:6.1.0"
     "mpich:3.1.4"
     "wget:1.16.3"
     "flex:2.6.0"

doc/dependency_tree/opencoarrays/mpich-3.1.4/gcc-5.1.0/mpc/.gitkeep

@@ -134,7 +134,7 @@ find_or_install()
         stack_push dependency_path "none" "$(./build.sh -P "$package")" "$(./build.sh -P gcc)"
       else
         printf "yes.\n"
-        echo -e "$this_script: Checking whether $executable in PATH wraps gfortran version 5.3.0 or later... "
+        echo -e "$this_script: Checking whether $executable in PATH wraps gfortran version `./build.sh -V gcc` or later... "
         $executable acceptable_compiler.f90 -o acceptable_compiler
         $executable print_true.f90 -o print_true
         acceptable=$(./acceptable_compiler)
@@ -203,7 +203,7 @@ find_or_install()
       stack_push dependency_path "none"
 
     elif [[ "$package_in_path" == "true" ]]; then
-      echo -e "$this_script: Checking whether $executable in PATH is version 5.3.0 or later..."
+      echo -e "$this_script: Checking whether $executable in PATH is version `./build.sh -V gcc` or later..."
       $executable -o acceptable_compiler acceptable_compiler.f90
       $executable -o print_true print_true.f90
       is_true=$(./print_true)

doc/dependency_tree/opencoarrays/mpich-3.1.4/gcc-5.1.0/mpfr/.gitkeep

@@ -3,15 +3,14 @@ print_header()
 {
   clear
   echo ""
-  echo "*** A default build of OpenCoarrays requires CMake 3.4.0 or later     ***"
-  echo "*** and MPICH 3.1.4 wrapping GCC Fortran (gfortran) 5.3.0 or later.   ***"
-  echo "*** Additionally, CMake, MPICH, and GCC have their own prerequisites. ***"
-  echo "*** This script will check for most known requirements in your PATH   ***"
-  echo "*** environment variable and in the default installation directory    ***"
-  echo "*** to which this script installs each missing prerequisite.  The     ***"
-  echo "*** script will recursively traverse the following dependency tree    ***"
-  echo "*** and ask permission to download, build, and install any missing    ***"
-  echo "*** prerequisites:                                                    ***"
+  echo "*** By default, building OpenCoarrays requires CMake 3.4.0 or later,      ***"
+  echo "*** MPICH 3.1.4, and GCC Fortran (gfortran) 6.1.0 or later.  To see       ***"
+  echo "*** options for forcing the use of older or alternative packages, execute ***"
+  echo "*** this script with the -h flag.  This script will recursively traverse  ***"
+  echo "*** the following dependency tree, asking permission to download, build,  ***"
+  echo "*** and install any packages that are required for building another       ***"
+  echo "*** package and are neither in your PATH nor in                           ***"
+  echo "*** opencoarrays/prerequisites/installations:                             ***"
   echo ""
   # Move to a directory tree whose structure mirrors the dependency tree
   pushd "$opencoarrays_src_dir/doc/dependency_tree/" > /dev/null
@@ -24,9 +23,8 @@ print_header()
   fi
   popd > /dev/null
   echo ""
-  printf "*** OpenCoarrays and all prerequisites will be downloaded, built, and installed in ***\n"
-  echo -e "${build_path}\n"
-  echo -e "${install_path}\n"
+  printf "${arg_p} will be installed in ${install_path}\n"
+  echo ""
   printf "Ready to rock and roll? (Y/n)"
   read -r install_now
   echo -e " $install_now\n"