Always use our own versions of *printf().

We've spent an awful lot of effort over the years in coping with
platform-specific vagaries of the *printf family of functions.  Let's just
forget all that mess and standardize on always using src/port/snprintf.c.
This gets rid of a lot of configure logic, and it will allow a saner
approach to dealing with %m (though actually changing that is left for
a follow-on patch).

Preliminary performance testing suggests that as it stands, snprintf.c is
faster than the native printf functions for some tasks on some platforms,
and slower for other cases.  A pending patch will improve that, though
cases with floating-point conversions will doubtless remain slower unless
we want to put a *lot* of effort into that.  Still, we've not observed
that *printf is really a performance bottleneck for most workloads, so
I doubt this matters much.

Patch by me, reviewed by Michael Paquier

Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us

src/interfaces/ecpg/compatlib/Makefile

@@ -31,7 +31,8 @@ SHLIB_EXPORTS = exports.txt
 # Need to recompile any libpgport object files
 LIBS := $(filter-out -lpgport, $(LIBS))
 
-OBJS= informix.o strerror.o $(filter snprintf.o strnlen.o, $(LIBOBJS)) $(WIN32RES)
+OBJS= informix.o snprintf.o strerror.o \
+	$(filter strnlen.o, $(LIBOBJS)) $(WIN32RES)
 
 PKG_CONFIG_REQUIRES_PRIVATE = libecpg libpgtypes
 

src/interfaces/ecpg/ecpglib/Makefile

@@ -26,8 +26,8 @@ override CFLAGS += $(PTHREAD_CFLAGS)
 LIBS := $(filter-out -lpgport, $(LIBS))
 
 OBJS= execute.o typename.o descriptor.o sqlda.o data.o error.o prepare.o memory.o \
-	connect.o misc.o path.o pgstrcasecmp.o strerror.o \
-	$(filter snprintf.o strlcpy.o strnlen.o win32setlocale.o isinf.o, $(LIBOBJS)) \
+	connect.o misc.o path.o pgstrcasecmp.o snprintf.o strerror.o \
+	$(filter strlcpy.o strnlen.o win32setlocale.o isinf.o, $(LIBOBJS)) \
 	$(WIN32RES)
 
 # thread.c is needed only for non-WIN32 implementation of path.c

src/interfaces/ecpg/pgtypeslib/Makefile

@@ -30,8 +30,8 @@ SHLIB_LINK += $(filter -lm, $(LIBS))
 SHLIB_EXPORTS = exports.txt
 
 OBJS= numeric.o datetime.o common.o dt_common.o timestamp.o interval.o \
-	pgstrcasecmp.o strerror.o \
-	$(filter rint.o snprintf.o strnlen.o, $(LIBOBJS)) \
+	pgstrcasecmp.o snprintf.o strerror.o \
+	$(filter rint.o strnlen.o, $(LIBOBJS)) \
 	string.o \
 	$(WIN32RES)
 

src/interfaces/libpq/Makefile

@@ -36,9 +36,9 @@ OBJS=	fe-auth.o fe-auth-scram.o fe-connect.o fe-exec.o fe-misc.o fe-print.o fe-l
 	libpq-events.o
 # libpgport C files we always use
 OBJS += chklocale.o inet_net_ntop.o noblock.o pgstrcasecmp.o pqsignal.o \
-	strerror.o thread.o
+	snprintf.o strerror.o thread.o
 # libpgport C files that are needed if identified by configure
-OBJS += $(filter crypt.o getaddrinfo.o getpeereid.o inet_aton.o open.o system.o snprintf.o strlcpy.o strnlen.o win32error.o win32setlocale.o, $(LIBOBJS))
+OBJS += $(filter crypt.o getaddrinfo.o getpeereid.o inet_aton.o open.o system.o strlcpy.o strnlen.o win32error.o win32setlocale.o, $(LIBOBJS))
 
 ifeq ($(enable_strong_random), yes)
 OBJS += pg_strong_random.o