[Bug-guile-ncurses] configure doesn't check for libunistring

[Jan Synáček]

That results in a compilation failure when the development files of
the library are not installed on the system.

make[2]: Entering directory '/home/jsynacek/src/guile-ncurses-1.6/ncurses'
/bin/sh ../libtool  --tag=CC   --mode=compile gcc -DHAVE_CONFIG_H -I.
-I..  -I ../lib -pthread -I/usr/include/guile/2.0       -g -O2 -MT
libguile_ncurses_la-unicode.lo -MD -MP -MF
.deps/libguile_ncurses_la-unicode.Tpo -c -o
libguile_ncurses_la-unicode.lo `test -f 'unicode.c' || echo
'./'`unicode.c
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I.. -I ../lib -pthread
-I/usr/include/guile/2.0 -g -O2 -MT libguile_ncurses_la-unicode.lo -MD
-MP -MF .deps/libguile_ncurses_la-unicode.Tpo -c unicode.c  -fPIC
-DPIC -o .libs/libguile_ncurses_la-unicode.o
unicode.c:39:21: fatal error: uniconv.h: No such file or directory
compilation terminated.

Cheers,
-- 
Jan Synáček