libunistring: Fix build on Windows, when a libunistring is installed.
* lib/unicase.in.h: Include <unistring/woe32dll.h>.
(unicase_empty_prefix_context, unicase_empty_suffix_context): Declare
with GNULIB_UNICASE_..._DLL_VARIABLE.
* lib/unictype.in.h: Include <unistring/woe32dll.h>.
(UC_CATEGORY_*, UC_PROPERTY_*): Declare with
GNULIB_UNICTYPE_..._DLL_VARIABLE.
* lib/uninorm.in.h: Include <unistring/woe32dll.h>.
(unicode_normalization_form uninorm_nf*): Declare with
GNULIB_UNINORM_..._DLL_VARIABLE.
* m4/libunistring-base.m4 (gl_LIBUNISTRING_MODULE_WITH_VARIABLE): New
macro.
(gl_LIBUNISTRING_LIB_PREPARE): Set HAVE_UNISTRING_WOE32DLL_H.
* m4/unicase_h.m4: New file.
* m4/unictype_h.m4: New file.
* m4/uninorm_h.m4: New file.
* modules/unicase/base (Files): Add m4/unicase_h.m4.
(configure.ac): Bump version number. Invoke gl_UNICASE_H,
gl_UNICASE_H_REQUIRE_DEFAULTS.
(Makefile.am): Substitute all GNULIB_UNICASE_*_DLL_VARIABLE.
* modules/unicase/empty-*-context (configure.ac): Invoke
gl_UNICASE_H_REQUIRE_DEFAULTS. Use gl_LIBUNISTRING_MODULE_WITH_VARIABLE.
* modules/unictype/base (Files): Add m4/unictype_h.m4.
(configure.ac): Bump version number. Invoke gl_UNICTYPE_H,
gl_UNICTYPE_H_REQUIRE_DEFAULTS.
(Makefile.am): Substitute all GNULIB_UNICTYPE_*_DLL_VARIABLE.
* modules/unictype/category-* (configure.ac): Invoke
gl_UNICTYPE_H_REQUIRE_DEFAULTS. Use
gl_LIBUNISTRING_MODULE_WITH_VARIABLE.
* modules/unictype/property-* (configure.ac): Likewise.
* modules/uninorm/base (Files): Add m4/uninorm_h.m4.
(configure.ac): Bump version number. Invoke gl_UNINORM_H,
gl_UNINORM_H_REQUIRE_DEFAULTS.
(Makefile.am): Substitute all GNULIB_UNINORM_*_DLL_VARIABLE.
* modules/uninorm/nf* (configure.ac): Invoke
gl_UNINORM_H_REQUIRE_DEFAULTS. Use gl_LIBUNISTRING_MODULE_WITH_VARIABLE.