Update configure to make it idempotent again and add MidnightBSD

Signed-off-by: Laslo Hunhold <dev@frign.de>

configure

diff --git a/configure b/configure
index 69df018..0f5e650 100755
--- a/configure
+++ b/configure
@@ -11,12 +11,12 @@
 }
 
 case $(uname) in
-	DragonFly|FreeBSD|Linux|NetBSD)
+	DragonFly|FreeBSD|Linux|MidnightBSD|NetBSD)
 		# the default
 		replace_line 'SOFLAGS'   '  '  '-shared -nostdlib -Wl,--soname=libgrapheme.so.$(VERSION_MAJOR).$(VERSION_MINOR)'
 		replace_line 'SONAME'    '   ' 'libgrapheme.so.$(VERSION_MAJOR).$(VERSION_MINOR).$(VERSION_PATCH)'
 		replace_line 'SOSYMLINK' ''    'true'
-		replace_line 'LDCONFIG'  ''    'ldconfig \# unset to not call ldconfig(1) after install/uninstall'
+		replace_line 'LDCONFIG'  ''    'ldconfig'
 		;;
 	OpenBSD)
 		replace_line 'SOFLAGS'   '  '  '-shared -nostdlib'