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/libinterp/find-defun-files.sh	Tue Feb 16 17:57:07 2016 -0800
+++ b/libinterp/find-defun-files.sh	Tue Feb 16 18:36:00 2016 -0800
@@ -1,6 +1,7 @@
 #! /bin/sh
 
 set -e
+
 SED=${SED:-sed}
 EGREP=${EGREP:-egrep}
 
@@ -11,7 +12,9 @@
 DEFUN_PATTERN="^[ \t]*DEF(CONSTFUN|CMD|UN|UN_DLD|UNX_DLD|UN_TEXT)[ \t]*\\("
 
 srcdir="$1"
-shift
+if [ "$1" ]; then
+  shift
+fi
 
 for arg
 do