Put CURLDEBUG and DEBUGBUILD in lib/curl_config.h.

[gevaerts]

This ensures that make dependency tracking will force a rebuild whenever
configure --enable-debug or --enable-curldebug changes.

The defines are still passed on the compiler commandline as well. That's
not ideal, but the m4 code is a bit daunting.

[bagder]

I ripped them out like this (after I applied your comit) and I see no issues:

diff --git a/m4/curl-compilers.m4 b/m4/curl-compilers.m4
index 20bdbd706..c1ae6a559 100644
--- a/m4/curl-compilers.m4
+++ b/m4/curl-compilers.m4
@@ -3,11 +3,11 @@
 #  Project                     ___| | | |  _ \| |
 #                             / __| | | | |_) | |
 #                            | (__| |_| |  _ <| |___
 #                             \___|\___/|_| \_\_____|
 #
-# Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+# Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
 #
 # This software is licensed as described in the file COPYING, which
 # you should have received as part of this distribution. The terms
 # are also available at https://curl.haxx.se/docs/copyright.html.
 #
@@ -1297,19 +1297,10 @@ AC_DEFUN([CURL_CHECK_CURLDEBUG], [
     if test "$supports_curldebug" = "no"; then
       AC_MSG_WARN([cannot enable curl debug memory tracking.])
       want_curldebug="no"
     fi
   fi
-  #
-  if test "$want_curldebug" = "yes"; then
-    CPPFLAGS="-DCURLDEBUG $CPPFLAGS"
-    squeeze CPPFLAGS
-  fi
-  if test "$want_debug" = "yes"; then
-    CPPFLAGS="-DDEBUGBUILD $CPPFLAGS"
-    squeeze CPPFLAGS
-  fi
 ])
 
 
 
 dnl CURL_CHECK_COMPILER_HALT_ON_ERROR

[gevaerts]

OK, I've added that to the commit.