Don't override CFLAGS etc in configure-generated makefile

CPPFLAGS, CFLAGS, CXXFLAGS and LDFLAGS are supposed to be under
user-control and putting configure-determined options in them broke
something as simple as running "make CXXFLAGS=-Wno-some-extra-warning"
because this overrode the CXXFLAGS set by configure and required for
build.

Improve this by using WX_*FLAGS in the generated makefile and leaving
the user-controlled FLAGS alone. This is still not ideal as running
"configure CFLAGS=-DFOO" and then "make CFLAGS=-DBAR" will define both
FOO and BAR, as configure copies CFLAGS to WX_CFLAGS, and so setting it
on make command line won't override it, as it should, but this should be
a much more rare and also much less severe problem, so we should be able
to live with it for now.

Normally this commit shouldn't result in any user-visible changes, i.e.
it shouldn't break any previously working scenarios and only make some
previously broken ones work.

configure

@@ -639,11 +639,15 @@ GUIDIST
 WXCONFIG_RESFLAGS
 WXCONFIG_LDFLAGS_GUI
 WXCONFIG_LDFLAGS
+WX_LDFLAGS
 WXCONFIG_RPATH
 WXCONFIG_LIBS
 WXCONFIG_CXXFLAGS
+WX_CXXFLAGS
 WXCONFIG_CFLAGS
+WX_CFLAGS
 WXCONFIG_CPPFLAGS
+WX_CPPFLAGS
 WX_CHARTYPE
 WX_SUBVERSION
 WX_VERSION
@@ -905,7 +909,6 @@ EXTRALIBS_MEDIA
 EXTRALIBS_HTML
 EXTRALIBS_XML
 EXTRALIBS
-CXXWARNINGS
 USE_PLUGINS
 MONOLITHIC
 WXUNIV
@@ -3802,6 +3805,11 @@ wx_top_builddir="`pwd -W 2> /dev/null || pwd`"
 
 
 
+USER_CPPFLAGS=$CPPFLAGS
+USER_CFLAGS=$CFLAGS
+USER_CXXFLAGS=$CXXFLAGS
+USER_LDFLAGS=$LDFLAGS
+
 
 USE_UNIX=1
 USE_WIN32=0
@@ -37720,7 +37728,7 @@ CPPFLAGS=`echo $WXCONFIG_CPPFLAGS \
 
 C_AND_CXX_FLAGS="$DEBUG_CFLAGS $PROFILE_FLAGS $OPTIMISE_CFLAGS"
 CFLAGS=`echo $WXCONFIG_CFLAGS $CWARNINGS $C_AND_CXX_FLAGS $CFLAGS `
-CXXFLAGS=`echo $WXCONFIG_CXXFLAGS $C_AND_CXX_FLAGS $CXXFLAGS `
+CXXFLAGS=`echo $WXCONFIG_CXXFLAGS $CXXWARNINGS $C_AND_CXX_FLAGS $CXXFLAGS `
 OBJCFLAGS=`echo $WXCONFIG_CFLAGS $CWARNINGS $C_AND_CXX_FLAGS $OBJCFLAGS `
 OBJCXXFLAGS=`echo $WXCONFIG_CXXFLAGS $C_AND_CXX_FLAGS $OBJCXXFLAGS `
 
@@ -37876,7 +37884,6 @@ fi
 
 
 
-
 
 
 TOOLKIT_LOWERCASE=`echo $TOOLKIT | tr '[A-Z]' '[a-z]'`
@@ -40366,8 +40373,18 @@ case "${host}" in
         ;;
 esac
 
-CFLAGS="$CFLAGS $CFLAGS_VISIBILITY"
-CXXFLAGS="$CXXFLAGS $CXXFLAGS_VISIBILITY"
+WX_CPPFLAGS=$CPPFLAGS
+WX_CFLAGS=$CFLAGS
+WX_CXXFLAGS=$CXXFLAGS
+WX_LDFLAGS=$LDFLAGS
+
+CPPFLAGS=$USER_CPPFLAGS
+CFLAGS=$USER_CFLAGS
+CXXFLAGS=$USER_CXXFLAGS
+LDFLAGS=$USER_LDFLAGS
+
+WX_CFLAGS="$WX_CFLAGS $CFLAGS_VISIBILITY"
+WX_CXXFLAGS="$WX_CXXFLAGS $CXXFLAGS_VISIBILITY"
 OBJCFLAGS="$OBJCFLAGS $CFLAGS_VISIBILITY"
 OBJCXXFLAGS="$OBJCXXFLAGS $CXXFLAGS_VISIBILITY"
 
@@ -40415,6 +40432,9 @@ SAMPLES_SUBDIRS="`echo $SAMPLES_SUBDIRS | tr -s ' ' | tr ' ' '\n' | sort | uniq
 
 
 
+
+
+