Apply PGDLLIMPORT markings to some GUC variables

According to the commit message in 8ec5694, we must have all variables
in header files marked with PGDLLIMPORT. In commit d3cc5ff some
variables were moved from launch_backend.c file to several header files.

This adds PGDLLIMPORT to moved variables.

Author: Sofia Kopikova <s.kopikova@postgrespro.ru>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/e0b17014-5319-4dd6-91cd-93d9c8fc9539%40postgrespro.ru

Author: petere

src/include/postmaster/syslogger.h

@@ -76,7 +76,7 @@ extern PGDLLIMPORT bool Log_truncate_on_rotation;
 extern PGDLLIMPORT int Log_file_mode;
 
 #ifdef EXEC_BACKEND
-extern pg_time_t first_syslogger_file_time;
+extern PGDLLIMPORT pg_time_t first_syslogger_file_time;
 #endif
 
 #ifndef WIN32

src/include/storage/pmsignal.h

@@ -58,7 +58,7 @@ typedef enum
 typedef struct PMSignalData PMSignalData;
 
 #ifdef EXEC_BACKEND
-extern volatile PMSignalData *PMSignalState;
+extern PGDLLIMPORT volatile PMSignalData *PMSignalState;
 #endif
 
 /*

src/include/storage/proc.h

@@ -454,8 +454,8 @@ extern PGDLLIMPORT int IdleSessionTimeout;
 extern PGDLLIMPORT bool log_lock_waits;
 
 #ifdef EXEC_BACKEND
-extern slock_t *ProcStructLock;
-extern PGPROC *AuxiliaryProcs;
+extern PGDLLIMPORT slock_t *ProcStructLock;
+extern PGDLLIMPORT PGPROC *AuxiliaryProcs;
 #endif
 
 

src/include/storage/procsignal.h

@@ -77,7 +77,7 @@ extern void procsignal_sigusr1_handler(SIGNAL_ARGS);
 typedef struct ProcSignalHeader ProcSignalHeader;
 
 #ifdef EXEC_BACKEND
-extern ProcSignalHeader *ProcSignal;
+extern PGDLLIMPORT ProcSignalHeader *ProcSignal;
 #endif
 
 #endif							/* PROCSIGNAL_H */

src/include/utils/guc.h

@@ -312,11 +312,11 @@ extern PGDLLIMPORT bool optimize_bounded_sort;
  * that would then require including the definition of struct
  * config_enum_entry into those header files.)
  */
-extern const struct config_enum_entry archive_mode_options[];
-extern const struct config_enum_entry dynamic_shared_memory_options[];
-extern const struct config_enum_entry recovery_target_action_options[];
-extern const struct config_enum_entry wal_level_options[];
-extern const struct config_enum_entry wal_sync_method_options[];
+extern PGDLLIMPORT const struct config_enum_entry archive_mode_options[];
+extern PGDLLIMPORT const struct config_enum_entry dynamic_shared_memory_options[];
+extern PGDLLIMPORT const struct config_enum_entry recovery_target_action_options[];
+extern PGDLLIMPORT const struct config_enum_entry wal_level_options[];
+extern PGDLLIMPORT const struct config_enum_entry wal_sync_method_options[];
 
 /*
  * Functions exported by guc.c