Clean up ICU includes.

Remove ICU includes from pg_locale.h, and instead include them in the
few C files that need ICU. Clean up a few other includes in passing.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/48911db71d953edec66df0d2ce303563d631fbe0.camel@j-davis.com

src/backend/commands/collationcmds.c

@@ -14,6 +14,10 @@
  */
 #include "postgres.h"
 
+#ifdef USE_ICU
+#include <unicode/uloc.h>
+#endif
+
 #include "access/htup_details.h"
 #include "access/table.h"
 #include "access/xact.h"

src/backend/utils/adt/formatting.c

@@ -68,17 +68,9 @@
 #include <math.h>
 #include <float.h>
 #include <limits.h>
-#include <wctype.h>
 
-#ifdef USE_ICU
-#include <unicode/ustring.h>
-#endif
-
-#include "catalog/pg_collation.h"
 #include "catalog/pg_type.h"
 #include "common/int.h"
-#include "common/unicode_case.h"
-#include "common/unicode_category.h"
 #include "mb/pg_wchar.h"
 #include "nodes/miscnodes.h"
 #include "parser/scansup.h"

src/backend/utils/adt/pg_locale.c

@@ -32,6 +32,9 @@
 #include "postgres.h"
 
 #include <time.h>
+#ifdef USE_ICU
+#include <unicode/ucol.h>
+#endif
 
 #include "access/htup_details.h"
 #include "catalog/pg_collation.h"
@@ -1645,6 +1648,17 @@ pg_towlower(pg_wchar wc, pg_locale_t locale)
 		return locale->ctype->wc_tolower(wc, locale);
 }
 
+/* version of Unicode used by ICU */
+const char *
+pg_icu_unicode_version()
+{
+#ifdef USE_ICU
+	return U_UNICODE_VERSION;
+#else
+	return NULL;
+#endif
+}
+
 /*
  * Return required encoding ID for the given locale, or -1 if any encoding is
  * valid for the locale.

src/backend/utils/adt/pg_locale_icu.c

@@ -12,7 +12,9 @@
 #include "postgres.h"
 
 #ifdef USE_ICU
+#include <unicode/ucasemap.h>
 #include <unicode/ucnv.h>
+#include <unicode/ucol.h>
 #include <unicode/ustring.h>
 
 /*

src/backend/utils/adt/varlena.c

@@ -5381,11 +5381,12 @@ unicode_version(PG_FUNCTION_ARGS)
 Datum
 icu_unicode_version(PG_FUNCTION_ARGS)
 {
-#ifdef USE_ICU
-	PG_RETURN_TEXT_P(cstring_to_text(U_UNICODE_VERSION));
-#else
-	PG_RETURN_NULL();
-#endif
+	const char *version = pg_icu_unicode_version();
+
+	if (version)
+		PG_RETURN_TEXT_P(cstring_to_text(version));
+	else
+		PG_RETURN_NULL();
 }
 
 /*

src/include/utils/pg_locale.h

@@ -14,16 +14,6 @@
 
 #include "mb/pg_wchar.h"
 
-#ifdef USE_ICU
-/* only include the C APIs, to avoid errors in cpluspluscheck */
-#undef U_SHOW_CPLUSPLUS_API
-#define U_SHOW_CPLUSPLUS_API 0
-#undef U_SHOW_CPLUSPLUS_HEADER_API
-#define U_SHOW_CPLUSPLUS_HEADER_API 0
-#include <unicode/ucol.h>
-#include <unicode/ucasemap.h>
-#endif
-
 /* use for libc locale names */
 #define LOCALE_NAME_BUFLEN 128
 
@@ -167,9 +157,9 @@ struct pg_locale_struct
 		struct
 		{
 			const char *locale;
-			UCollator  *ucol;
+			struct UCollator *ucol;
+			struct UCaseMap *ucasemap;
 			locale_t	lt;
-			UCaseMap   *ucasemap;
 		}			icu;
 #endif
 	};
@@ -223,6 +213,8 @@ extern bool pg_iswcased(pg_wchar wc, pg_locale_t locale);
 extern pg_wchar pg_towupper(pg_wchar wc, pg_locale_t locale);
 extern pg_wchar pg_towlower(pg_wchar wc, pg_locale_t locale);
 
+extern const char *pg_icu_unicode_version(void);
+
 extern int	builtin_locale_encoding(const char *locale);
 extern const char *builtin_validate_locale(int encoding, const char *locale);
 extern void icu_validate_locale(const char *loc_str);