Fix inconsistencies in the code

This addresses a couple of issues in the code:
- Typos and inconsistencies in comments and function declarations.
- Removal of unreferenced function declarations.
- Removal of unnecessary compile flags.
- A cleanup error in regressplans.sh.

Author: Alexander Lakhin
Discussion: https://postgr.es/m/0c991fdf-2670-1997-c027-772a420c4604@gmail.com

src/interfaces/ecpg/compatlib/exports.txt

@@ -1,5 +1,5 @@
 # src/interfaces/ecpg/compatlib/exports.txt
-# Functions to be exported by ecpg_compatlib DLL
+# Functions to be exported by libecpg_compat DLL
 ECPG_informix_get_var   1
 ECPG_informix_set_var   2
 decadd                  3

src/interfaces/ecpg/ecpglib/ecpglib_extern.h

@@ -195,11 +195,8 @@ char	   *ecpg_strdup(const char *, int);
 const char *ecpg_type_name(enum ECPGttype);
 int			ecpg_dynamic_type(Oid);
 int			sqlda_dynamic_type(Oid, enum COMPAT_MODE);
-void		ecpg_free_auto_mem(void);
 void		ecpg_clear_auto_mem(void);
 
-struct descriptor *ecpggetdescp(int, char *);
-
 struct descriptor *ecpg_find_desc(int line, const char *name);
 
 struct prepared_statement *ecpg_find_prepared_statement(const char *,

src/interfaces/ecpg/ecpglib/execute.c

@@ -1899,7 +1899,7 @@ ecpg_process_output(struct statement *stmt, bool clear_result)
 
 			/*
 			 * execution should never reach this code because it is already
-			 * handled in ECPGcheck_PQresult()
+			 * handled in ecpg_check_PQresult()
 			 */
 			ecpg_log("ecpg_process_output on line %d: unknown execution status type\n",
 					 stmt->lineno);

src/interfaces/ecpg/include/ecpglib.h

@@ -63,8 +63,6 @@ char	   *ECPGprepared_statement(const char *, const char *, int);
 PGconn	   *ECPGget_PGconn(const char *);
 PGTransactionStatusType ECPGtransactionStatus(const char *);
 
-char	   *ECPGerrmsg(void);
-
  /* print an error message */
 void		sqlprint(void);
 

src/interfaces/ecpg/preproc/Makefile

@@ -19,7 +19,6 @@ override CPPFLAGS := -I../include -I$(top_srcdir)/src/interfaces/ecpg/include \
 	-I. -I$(srcdir) \
 	-I$(top_srcdir)/src/interfaces/ecpg/ecpglib \
 	-I$(libpq_srcdir) \
-	-DECPG_COMPILE \
 	$(CPPFLAGS)
 
 override CFLAGS += $(PTHREAD_CFLAGS)

src/interfaces/ecpg/preproc/preproc_extern.h

@@ -30,7 +30,6 @@ extern int	braces_open,
 			struct_level,
 			ecpg_internal_var;
 extern char *current_function;
-extern char *descriptor_index;
 extern char *descriptor_name;
 extern char *connection;
 extern char *input_filename;