Fixes #227

Because the new windows-install.sh uses Ubuntu 16.04, which comes with Windows Subsystem for Linux (WSL),
our Windows installer can be tested in Linux image on Travis-CI.  Our release notes should indicate
the following limitations:
1. The Windows installer builds the default GCC installed by apt-get, which is 5.4.0 for Ubuntu 16.04.
2. Ubuntu 16.04 comes with WSL releases 14936 or later.
3. Updating to 16.04 requires joining the Windows Insider Preview program, selecting "Fast" updates, and running do-release-upgrade.

Author: Damian Rouson

windows-install.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#/usr/bin/env bash
 #
 # windows-install.sh
 #
@@ -79,8 +79,6 @@
 # (3) Parse the usage information (default usage file name: current file's name with -usage appended).
 # (4) Parse the command line using the usage information.
 
-starting_directory=${PWD}
-
 ### Start of boilerplate -- do not edit this block #######################
 export OPENCOARRAYS_SRC_DIR="${OPENCOARRAYS_SRC_DIR:-${PWD%/}}"
 if [[ ! -f "${OPENCOARRAYS_SRC_DIR}/src/libcaf.h" ]]; then
@@ -246,34 +244,33 @@ else
     sudo apt-get install mpich
   fi
 
-  # Install OpenCoarrays
-
- 
-set_SUDO_if_needed_to_write_to_install_dir()
-{
-  info "Checking whether the directory ${install_prefix} exists... "
-  if [[ -d "${install_prefix}" ]]; then
-    info "yes"
-    info "Checking whether I have write permissions to ${install_prefix} ... "
-    if [[ -w "${install_prefix}" ]]; then
+  set_SUDO_if_needed_to_write_to_install_dir()
+  {
+    info "Checking whether the directory ${install_prefix} exists... "
+    if [[ -d "${install_prefix}" ]]; then
       info "yes"
+      info "Checking whether I have write permissions to ${install_prefix} ... "
+      if [[ -w "${install_prefix}" ]]; then
+        info "yes"
+      else
+        info "no"
+        SUDO="sudo"
+      fi
     else
       info "no"
-      SUDO="sudo"
-    fi
-  else
-    info "no"
-    info "Checking whether I can create ${install_prefix} ... "
-    if mkdir -p "${install_prefix}" >& /dev/null; then
-      info "yes."
-    else
-      info "no."
-      SUDO="sudo"
+      info "Checking whether I can create ${install_prefix} ... "
+      if mkdir -p "${install_prefix}" >& /dev/null; then
+        info "yes."
+      else
+        info "no."
+        SUDO="sudo"
+      fi
     fi
-  fi
-}
-set_SUDO_if_needed_to_write_to_install_dir
+  }
+  set_SUDO_if_needed_to_write_to_install_dir
 
+  # Install OpenCoarrays
+
   if [[ -d "$build_path" ]]; then
     rm -rf "$build_path"
   fi