configure: unify handling of xyzdir variables

Making an xyzdir variable for each directory prepares for the next
patches introducing config-host.h defines and configure options for them.
It also fixes the problem where overriding prefix at "make install"
time did not override it for sysconfdir.

Removes some of the differences between sysconfdir and other variables,
the rest will go away later.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

configure

@@ -1985,14 +1985,18 @@ else
   confsuffix="/qemu"
 fi
 
-: ${sysconfdir:="${prefix}$sysconfsuffix"}
+mandir="\${prefix}$mansuffix"
+datadir="\${prefix}$datasuffix"
+docdir="\${prefix}$docsuffix"
+bindir="\${prefix}$binsuffix"
+: ${sysconfdir:="\${prefix}$sysconfsuffix"}
 confdir=$sysconfdir$confsuffix
 
 echo "Install prefix    $prefix"
-echo "BIOS directory    $prefix$datasuffix"
-echo "binary directory  $prefix$binsuffix"
+echo "BIOS directory    `eval echo $datadir`"
+echo "binary directory  `eval echo $bindir`"
 if test "$mingw32" = "no" ; then
-echo "Manual directory  $prefix$mansuffix"
+echo "Manual directory  `eval echo $mandir`"
 echo "ELF interp prefix $interp_prefix"
 fi
 echo "Source path       $source_path"
@@ -2308,11 +2312,11 @@ fi
 echo "ROMS=$roms" >> $config_host_mak
 
 echo "prefix=$prefix" >> $config_host_mak
-echo "bindir=\${prefix}$binsuffix" >> $config_host_mak
-echo "mandir=\${prefix}$mansuffix" >> $config_host_mak
-echo "datadir=\${prefix}$datasuffix" >> $config_host_mak
+echo "bindir=$bindir" >> $config_host_mak
+echo "mandir=$mandir" >> $config_host_mak
+echo "datadir=$datadir" >> $config_host_mak
 echo "sysconfdir=$sysconfdir" >> $config_host_mak
-echo "docdir=\${prefix}$docsuffix" >> $config_host_mak
+echo "docdir=$docdir" >> $config_host_mak
 echo "MAKE=$make" >> $config_host_mak
 echo "INSTALL=$install" >> $config_host_mak
 echo "INSTALL_DIR=$install -d -m0755 -p" >> $config_host_mak