maint: Use consistent coding style for build helper shell scripts * mk-octave-config-h.sh: Keep if-then on a single line. * move-if-change: Insert a space in interpreter directive for consistency. * build-env-features.sh, config-images.sh, config-module.sh, config-ops.sh, find-defun-files.sh, find-files-with-tests.sh, mk-errno-list, libinterp/mk-pkg-add, scripts/mk-pkg-add, mkbuiltins, mkdefs, mkdocs, mkf77def.in, mkops: Initialize environment variable defaults consistently. Use shift only when the argument list is not empty. Remove unnecessary quotes and semicolons on variable assignments. Insert/remove blank lines for consistency.

--- a/build-aux/move-if-change	Tue Feb 16 17:57:07 2016 -0800
+++ b/build-aux/move-if-change	Tue Feb 16 18:36:00 2016 -0800
@@ -1,4 +1,4 @@
-#!/bin/sh
+#! /bin/sh
 #
 # Like mv $1 $2, but if the files are the same, just delete $1.
 # Status is 0 if $2 is changed, 1 otherwise.