Blender Git Loki

UI: avoid excessive padding for labels in headers

Labels in headers reserved space for an icon even when no icon was used.

This is caused by the shared function ui_text_icon_width adding 1.5x
a buttons X-units width the the width of the string.

Menu buttons detected this and subtracted the extra padding.

Instead of adding the same workaround for labels,
add ui_text_icon_width_ex that takes a padding argument.

Add presets for 'default', 'compact' and 'none' to avoid duplicating
padding values.

This allows removal of hard-coded label scaling for the add-object tool.