[WIP] Fix HAVE_CONFIG_H -Wundef warnings.

[Carlos O'Donell]

Roland,

Is fixing the HAVE_CONFIG_H -Wundef warnings as easy as this?

diff --git a/Makeconfig b/Makeconfig
index f965398..64b64fc 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -1081,6 +1081,9 @@ endif
 sysd-rules-targets := $(sort $(foreach p,$(sysd-rules-patterns),\
                                         $(firstword $(subst :, ,$p))))
 
+# We always configure glibc such that config.h is available.
+defines += -DHAVE_CONFIG_H=1
+
 # A sysdeps Makeconfig fragment may set libc-reentrant to yes.
 ifeq (yes,$(libc-reentrant))
 defines += -D_LIBC_REENTRANT
---

Followed by the mechanical change of all the `#idfef HAVE_CONFIG_H`
to `#if HAVE_CONFIG_H`.

Then verify the built binaries are identical and pass the testsuite?

We always create a config.h for glibc so this looks correct.

I don't want to waste my time fixing all of this if I've got it wrong.

Cheers,
Carlos.