config: Symlink config.h to config.def.h

config.h is created when making dwm (from config.def.h) if it does not
already exist, but it is not tracked by version control. By symlinking
the two, we can apply changes that relate to either file without issue.
build configuration: Remove Xinerama support

I currently only run dwm in single monitor configurations, so I don't
need this. If that situation changes, this commit should be reverted.
tagmon: Focus monitor after moving client
tag: Focus client after moving tag
layouts: Apply bstack patch

bstackhoriz is removed from this patch, as I don't use it.
stack: Apply attachaside patch
config: Use size 12 Terminus as font
config: Use i3-like colour scheme
config: Do not display bar
config: Do not respect resize hints

This allows urxvt to properly fill all of the available space.
spawn: Revert usage of dmenu's -m option

This is not available in the stable version of dmenu (currently 4.5).
This reversion should also itself be reverted once a version of dmenu
with -m arrives in the Arch Linux repositories.

This reverts commit 6af273771cb0e28e4394c78ab0322f77025a57f3.
config: Configure four tags and keybindings
config: Use urxvtc as terminal
keys: Use "q" to launch dmenu
keys: Do not require Shift to launch terminal
keys: Remove togglebar
keys: Navigate the stack with comma
keys: Remove incnmaster bindings
keys: Remove setmfact bindings
keys: Move client to master area with Mod+Tab