build: Modernize build system a bit
build: Modernize build system a bit

Use the tar-ustar option for AM_INIT_AUTOMAKE for better tarballs.
Do not use AM_MAINTAINER_MODE as it is not recommended by automake
developers.
Stop using GNOME_COMMON_INIT as it is deprecated.
Use LT_PREREQ & LT_INIT for libtool checks.
Require intltool 0.40.6 to avoid various bugs.
Do not use AC_ISC_POSIX, AC_HEADER_STDC as they shouldn't be needed on
modern systems.
Drop manual check for additional compiler flags.

lanoxx/libwnck,lanoxx/libwnck