Revert "Provide DLLEXPORT markers for C functions via PG_FUNCTION_INFO_V1 macro."

This reverts commit c8ead2a3.
Seems there is no way to do this that doesn't cause MSVC to give
warnings, so let's just go back to the way we've been doing it.

Discussion: <11843.1478358206@sss.pgh.pa.us>

contrib/hstore/hstore.h

@@ -194,7 +194,7 @@ extern Pairs *hstoreArrayToPairs(ArrayType *a, int *npairs);
 #if HSTORE_POLLUTE_NAMESPACE
 #define HSTORE_POLLUTE(newname_,oldname_) \
 	PG_FUNCTION_INFO_V1(oldname_);		  \
-	extern PGDLLEXPORT Datum newname_(PG_FUNCTION_ARGS); \
+	Datum newname_(PG_FUNCTION_ARGS);	  \
 	Datum oldname_(PG_FUNCTION_ARGS) { return newname_(fcinfo); } \
 	extern int no_such_variable
 #else

contrib/ltree/ltree.h

@@ -130,30 +130,30 @@ typedef struct
 
 
 /* use in array iterator */
-extern PGDLLEXPORT Datum ltree_isparent(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum ltree_risparent(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum ltq_regex(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum ltq_rregex(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum lt_q_regex(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum lt_q_rregex(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum ltxtq_exec(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum ltxtq_rexec(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum _ltq_regex(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum _ltq_rregex(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum _lt_q_regex(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum _lt_q_rregex(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum _ltxtq_exec(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum _ltxtq_rexec(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum _ltree_isparent(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum _ltree_risparent(PG_FUNCTION_ARGS);
+Datum		ltree_isparent(PG_FUNCTION_ARGS);
+Datum		ltree_risparent(PG_FUNCTION_ARGS);
+Datum		ltq_regex(PG_FUNCTION_ARGS);
+Datum		ltq_rregex(PG_FUNCTION_ARGS);
+Datum		lt_q_regex(PG_FUNCTION_ARGS);
+Datum		lt_q_rregex(PG_FUNCTION_ARGS);
+Datum		ltxtq_exec(PG_FUNCTION_ARGS);
+Datum		ltxtq_rexec(PG_FUNCTION_ARGS);
+Datum		_ltq_regex(PG_FUNCTION_ARGS);
+Datum		_ltq_rregex(PG_FUNCTION_ARGS);
+Datum		_lt_q_regex(PG_FUNCTION_ARGS);
+Datum		_lt_q_rregex(PG_FUNCTION_ARGS);
+Datum		_ltxtq_exec(PG_FUNCTION_ARGS);
+Datum		_ltxtq_rexec(PG_FUNCTION_ARGS);
+Datum		_ltree_isparent(PG_FUNCTION_ARGS);
+Datum		_ltree_risparent(PG_FUNCTION_ARGS);
 
 /* Concatenation functions */
-extern PGDLLEXPORT Datum ltree_addltree(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum ltree_addtext(PG_FUNCTION_ARGS);
-extern PGDLLEXPORT Datum ltree_textadd(PG_FUNCTION_ARGS);
+Datum		ltree_addltree(PG_FUNCTION_ARGS);
+Datum		ltree_addtext(PG_FUNCTION_ARGS);
+Datum		ltree_textadd(PG_FUNCTION_ARGS);
 
 /* Util function */
-extern PGDLLEXPORT Datum ltree_in(PG_FUNCTION_ARGS);
+Datum		ltree_in(PG_FUNCTION_ARGS);
 
 bool ltree_execute(ITEM *curitem, void *checkval,
 			  bool calcnot, bool (*chkcond) (void *checkval, ITEM *val));

doc/src/sgml/xfunc.sgml

@@ -2577,23 +2577,6 @@ concat_text(PG_FUNCTION_ARGS)
         error messages to this effect.
        </para>
       </listitem>
-
-      <listitem>
-       <para>
-        To work correctly on Windows, <literal>C</>-language functions need
-        to be marked with <literal>PGDLLEXPORT</>, unless you use a build
-        process that marks all global functions that way.  In simple cases
-        this detail will be handled transparently by
-        the <literal>PG_FUNCTION_INFO_V1</> macro.  However, if you write
-        explicit external declarations (perhaps in header files), be sure
-        to write them like this:
-<programlisting>
-extern PGDLLEXPORT Datum funcname(PG_FUNCTION_ARGS);
-</programlisting>
-        or you'll get compiler complaints when building on Windows.  (On
-        other platforms, the <literal>PGDLLEXPORT</> macro does nothing.)
-       </para>
-      </listitem>
      </itemizedlist>
     </para>
    </sect2>

src/include/fmgr.h

@@ -350,11 +350,12 @@ typedef const Pg_finfo_record *(*PGFInfoFunction) (void);
  *
  *	On Windows, the function and info function must be exported.  Our normal
  *	build processes take care of that via .DEF files or --export-all-symbols.
- *	Module authors using a different build process might do it differently,
- *	so we declare these functions PGDLLEXPORT for their convenience.
+ *	Module authors using a different build process might need to manually
+ *	declare the function PGDLLEXPORT.  We do that automatically here for the
+ *	info function, since authors shouldn't need to be explicitly aware of it.
  */
 #define PG_FUNCTION_INFO_V1(funcname) \
-extern PGDLLEXPORT Datum funcname(PG_FUNCTION_ARGS); \
+extern Datum funcname(PG_FUNCTION_ARGS); \
 extern PGDLLEXPORT const Pg_finfo_record * CppConcat(pg_finfo_,funcname)(void); \
 const Pg_finfo_record * \
 CppConcat(pg_finfo_,funcname) (void) \