Fix some missing .gitignore and "make clean" items in ecpg.

Some of the files we optionally link in from elsewhere weren't ignored
and/or weren't cleaned up at "make clean".  Noted while testing on a
machine that needs our version of snprintf.c.

src/interfaces/ecpg/compatlib/.gitignore

 /compatlib.def
 /blibecpg_compatdll.def
 /exports.list
+/snprintf.c

src/interfaces/ecpg/ecpglib/.gitignore

 /ecpglib.def
 /blibecpgdll.def
 /exports.list
-
 /path.c
 /pgstrcasecmp.c
+/snprintf.c
 /strlcpy.c
 /thread.c
+/win32setlocale.c
+/isinf.c

src/interfaces/ecpg/ecpglib/Makefile

@@ -76,6 +76,6 @@ uninstall: uninstall-lib
 
 clean distclean: clean-lib
 	rm -f $(OBJS)
-	rm -f path.c pgstrcasecmp.c snprintf.c strlcpy.c thread.c win32setlocale.c
+	rm -f path.c pgstrcasecmp.c snprintf.c strlcpy.c thread.c win32setlocale.c isinf.c
 
 maintainer-clean: distclean maintainer-clean-lib

src/interfaces/ecpg/pgtypeslib/.gitignore

 /pgtypeslib.def
 /blibpgtypesdll.def
 /exports.list
-
 /pgstrcasecmp.c
+/rint.c
+/snprintf.c