configure.ac: improve shell compatibility, generate package version components at autoconf time

configure.ac

@@ -73,9 +73,9 @@ MHD_SYS_EXT
 LT_INIT([win32-dll])
 LT_LANG([Windows Resource])
 
-PACKAGE_VERSION_MAJOR=${PACKAGE_VERSION%.*.*}
-PACKAGE_VERSION_MINOR=${PACKAGE_VERSION%.*}; PACKAGE_VERSION_MINOR=${PACKAGE_VERSION_MINOR#*.}
-PACKAGE_VERSION_SUBMINOR=${PACKAGE_VERSION#*.*.}
+PACKAGE_VERSION_MAJOR='m4_car(m4_unquote(m4_split(AC_PACKAGE_VERSION, [\.])))'
+PACKAGE_VERSION_MINOR='m4_argn(2, m4_unquote(m4_split(AC_PACKAGE_VERSION, [\.])))'
+PACKAGE_VERSION_SUBMINOR='m4_argn(3, m4_unquote(m4_split(AC_PACKAGE_VERSION, [\.])))'
 AC_SUBST([PACKAGE_VERSION_MAJOR])
 AC_SUBST([PACKAGE_VERSION_MINOR])
 AC_SUBST([PACKAGE_VERSION_SUBMINOR])