Add the Portugese/Spanish keymap. Similarly to the Finnish/Swedish
keymap, it's compatible with both Portugese and Spanish keyboards.

Also, modify x11-keymap so that the Portugese/Spanish map will use
Alt+Shift to enter an underscore in the F key and a backslash in the C
key, which was done to avoid redundancy with the "Ñ" key.

Signed-off-by: Lux Aliaga <lux@nixgoat.me>

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