libphobos: Bump soname version to 5 [PR113667]

Each major release is not binary compatible with the previous.

	PR d/113667

libphobos/ChangeLog:

	* configure: Regenerate.
	* configure.ac (libtool_VERSION): Update to 5:0:0.

libphobos/configure

@@ -15741,7 +15741,7 @@ SPEC_PHOBOS_DEPS="$LIBS"
 # Libdruntime / phobos soname version
-libtool_VERSION=4:0:0
+libtool_VERSION=5:0:0
 # Set default flags (after DRUNTIME_WERROR!)

libphobos/configure.ac

@@ -258,7 +258,7 @@ SPEC_PHOBOS_DEPS="$LIBS"
 AC_SUBST(SPEC_PHOBOS_DEPS)
 
 # Libdruntime / phobos soname version
-libtool_VERSION=4:0:0
+libtool_VERSION=5:0:0
 AC_SUBST(libtool_VERSION)
 
 # Set default flags (after DRUNTIME_WERROR!)