Remove function declarations from headers for some undefined functions

The functions whose declarations are removed here have been removed in
the past, but their respective headers forgot the call.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20230110045722.GD9837@telsasoft.com

src/bin/pg_dump/compress_io.h

@@ -54,8 +54,6 @@ typedef struct cfp cfp;
 
 extern cfp *cfopen(const char *path, const char *mode,
 				   const pg_compress_specification compression_spec);
-extern cfp *cfdopen(int fd, const char *mode,
-					pg_compress_specification compression_spec);
 extern cfp *cfopen_read(const char *path, const char *mode);
 extern cfp *cfopen_write(const char *path, const char *mode,
 						 const pg_compress_specification compression_spec);

src/include/access/gist_private.h

@@ -549,8 +549,6 @@ extern void gistSplitByKey(Relation r, Page page, IndexTuple *itup,
 /* gistbuild.c */
 extern IndexBuildResult *gistbuild(Relation heap, Relation index,
 								   struct IndexInfo *indexInfo);
-extern void gistValidateBufferingOption(const char *value);
-
 /* gistbuildbuffers.c */
 extern GISTBuildBuffers *gistInitBuildBuffers(int pagesPerBuffer, int levelStep,
 											  int maxLevel);

src/include/access/xlogreader.h

@@ -332,8 +332,6 @@ extern XLogReaderState *XLogReaderAllocate(int wal_segment_size,
 										   const char *waldir,
 										   XLogReaderRoutine *routine,
 										   void *private_data);
-extern XLogReaderRoutine *LocalXLogReaderRoutine(void);
-
 /* Free an XLogReader */
 extern void XLogReaderFree(XLogReaderState *state);