sch2fig/: rename "cairo" to "cro"

To avoid confusion and possible clashes with the real Cairo.

sch2fig/Makefile

@@ -13,7 +13,7 @@
 NAME = sch2fig
 OBJS = main.o sch-parse.o sch-render.o lib-parse.o lib-render.o \
        file.o \
-       style.o fig.o record.o cairo.o diff.o gfx.o dwg.o text.o misc.o
+       style.o fig.o record.o cro.o diff.o gfx.o dwg.o text.o misc.o
 
 CFLAGS = -g  -Wall -Wextra -Wno-unused-parameter -Wshadow \
 	 -Wmissing-prototypes -Wmissing-declarations \