Stop using GNOME_COMMON_INIT as it is deprecated.
Do not use AM_MAINTAINER_MODE as it is not recommended by automake
developers.
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, AM_PROG_CC_C_O as they
shouldn't be needed on modern systems.
Remove checks for perl and awk, and the useless --disable-rebuilds
configure flag.