toggle border & resize dialog from env vars

[KebabLord]

If a user wants to resize or toggle the border of the prompt dialog window for aesthetic purposes, he has to update the macros, edit the XDrawRectangle function and compile the source code. This commit passes this job to these two new environmental variables:

• XSECURELOCK_SHOW_BORDER: whether to show the border of auth window. Disabled by default.
• XSECURELOCK_BORDER_SIZE: size of the auth dialog window. Defaults to 16 just like before.

for example

export XSECURELOCK_BORDER_SIZE=60
export XSECURELOCK_SHOW_BORDER=1

export XSECURELOCK_BORDER_SIZE=12
export XSECURELOCK_SHOW_BORDER=

[budRich]

judging by the screenshots XSECURELOCK_BORDER_SIZE and XSECURELOCK_SHOW_BORDER seems to affect two different visual elements, border and "padding". imo XSECURELOCK_BORDER_SIZE should be called XSECURELOCK_PADDING.

Sweet wallpaper!