gtk/inspector/css-node-tree.c: Fix Build
gtk/inspector/css-node-tree.c: Fix Build

strcasecmp() is unfortunately not universally available, along with
strings.h.  Fix the build by replacing strcasecmp() with
g_ascii_strcasecmp(), and remove the strings.h include.

https://bugzilla.gnome.org/show_bug.cgi?id=747604

alexlarsson/gtk,grubersjoe/adwaita,jigpu/gtk,jigpu/gtk,jigpu/gtk,chergert/gtk,chergert/gtk,chergert/gtk,davidgumberg/gtk,davidgumberg/gtk,grubersjoe/adwaita,alexlarsson/gtk,jigpu/gtk,alexlarsson/gtk,davidgumberg/gtk,alexlarsson/gtk,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,grubersjoe/adwaita,chergert/gtk,davidgumberg/gtk,jadahl/gtk,jadahl/gtk,Adamovskiy/gtk,jigpu/gtk,alexlarsson/gtk,Adamovskiy/gtk,alexlarsson/gtk,Adamovskiy/gtk,alexlarsson/gtk,davidgumberg/gtk,davidgumberg/gtk,Adamovskiy/gtk,Adamovskiy/gtk,jigpu/gtk,jadahl/gtk,Adamovskiy/gtk,chergert/gtk,grubersjoe/adwaita,Adamovskiy/gtk,jadahl/gtk,jadahl/gtk,Adamovskiy/gtk,grubersjoe/adwaita,chergert/gtk,jigpu/gtk,davidgumberg/gtk,grubersjoe/adwaita,jadahl/gtk,jadahl/gtk,jigpu/gtk,chergert/gtk,chergert/gtk