Un-break ecpg tests for Windows.

Declaring a function "inline" still doesn't work with Windows compilers
(C99? what's that?), unless the macro provided by pg_config.h is
in-scope, which it is not in our ECPG test programs.  So the workaround
I tried to use in commit 7640f931 doesn't work for Windows.  Revert
the change in printf_hack.h, and instead just blacklist that file
in cpluspluscheck --- since it's a not-installed test file, we don't
really need to verify its C++ cleanliness anyway.

src/interfaces/ecpg/test/expected/compat_informix-dec_test.c

@@ -33,7 +33,7 @@
  * print_double(x) has the same effect as printf("%g", x), but is intended
  * to produce the same formatting across all platforms.
  */
-static inline void
+static void
 print_double(double x)
 {
 #ifdef WIN32

src/interfaces/ecpg/test/expected/pgtypeslib-num_test.c

@@ -29,7 +29,7 @@
  * print_double(x) has the same effect as printf("%g", x), but is intended
  * to produce the same formatting across all platforms.
  */
-static inline void
+static void
 print_double(double x)
 {
 #ifdef WIN32

src/interfaces/ecpg/test/expected/pgtypeslib-num_test2.c

@@ -30,7 +30,7 @@
  * print_double(x) has the same effect as printf("%g", x), but is intended
  * to produce the same formatting across all platforms.
  */
-static inline void
+static void
 print_double(double x)
 {
 #ifdef WIN32

src/interfaces/ecpg/test/printf_hack.h

@@ -2,7 +2,7 @@
  * print_double(x) has the same effect as printf("%g", x), but is intended
  * to produce the same formatting across all platforms.
  */
-static inline void
+static void
 print_double(double x)
 {
 #ifdef WIN32

src/tools/pginclude/cpluspluscheck

@@ -105,6 +105,8 @@ do
 
 	# regression.h is not actually C, but ECPG code.
 	test "$f" = src/interfaces/ecpg/test/regression.h && continue
+	# printf_hack.h produces "unused function" warnings.
+	test "$f" = src/interfaces/ecpg/test/printf_hack.h && continue
 
 	# pg_trace.h and utils/probes.h can include sys/sdt.h from SystemTap,
 	# which itself contains C++ code and so won't compile with a C++