Improve bash quoting, and other similar best practices

This patch updates the shell scripts with some of the common best
practices, which should make them more resilient to unusual failures and
unexpected environments (in particular, directories with spaces).

Most of these were identified by shellcheck.

docs/man/generate.sh

@@ -8,20 +8,20 @@
 set -e
 
 for IN in *.pod; do
-	OUT=$( basename $IN .pod )
+	OUT=$(basename "$IN" .pod)
 	SECTION=${OUT##*.}
 	NAME=${OUT%.*}
 
 	# If it has not changed in git, set the mtime to the last commit that
 	# touched the file.
 	CHANGED=$( git status --porcelain -- "$IN" | wc -l )
-	if [ $CHANGED -eq 0 ]; then
+	if [ "$CHANGED" -eq 0 ]; then
 		GIT_MTIME=$( git log --pretty=%at -n1 -- "$IN" )
 		touch -d "@$GIT_MTIME" "$IN"
 	fi
 
-	podchecker $IN
-	pod2man --section=$SECTION --name=$NAME \
+	podchecker "$IN"
+	pod2man --section="$SECTION" --name="$NAME" \
 		--release "" --center "" \
-		$IN $OUT
+		"$IN" "$OUT"
 done