Add scripts for automating more parts of the release process

Update dates in various files before the release automatically.

Also automatically update SHA-1 of the release files both before the
release (to zero them) and afterwards (to use the correct values).

Closes https://github.com/wxWidgets/wxWidgets/pull/443

build/tools/post-release.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+# Exit immediately if a command exits with a non-zero status.
+set -e
+
+# Build the file list for sha1sums, from `docs/release.md`
+declare -a files=(`sed -n '/^## Download Verification/,/^## Binaries/p' ../../docs/release.md | sed -n -E 's/^\s*0{40}\s{2}(wx.*)/\1/p'`)
+
+# Get the release version
+ver_string=`grep '#define wxVERSION_STRING ' ./../../include/wx/version.h | sed 's/^.*"wxWidgets \(.*\)")/\1/'`
+
+for i in "${files[@]}"
+do
+    # compute sha1sum
+    sha1sum=`sha1sum ./../../distrib/release/$ver_string/$i`
+
+    # save the sha1sum for this file
+    sed -i -E "/^\s*[0]{40}\s{2}wx/ s/(^\s*)[0]{40}(\s{2}$i)/\1$sha1sum\2/" ./../../docs/release.md
+done
+
+# Commit sha1sum related changes
+git commit -m "Update released files sha1sums after $ver_string release" ./../../docs/release.md