configure: replace deprecated AM_CONFIG_HEADER with AC_CONFIG_HEADERS

AM_CONFIG_HEADER has been removed in the just-released automake 1.13:
https://lists.gnu.org/archive/html/automake/2012-12/msg00038.html

https://bugzilla.gnome.org/show_bug.cgi?id=690881
basesink: Check if buffers are too late before calling prepare/prepare_list

https://bugzilla.gnome.org/show_bug.cgi?id=690936
adapter: return gssize from gst_adapter_masked_scan_* functions

As the return value of this function is -1 when the match is not found
basesink: Initialize uninitialized variable
docs: minor systemsclock doc fix
tests: fix leak in ghostpad unit test

The created pad is never used and overwritten with
another newly-created pad a few lines below.
docs: improve api docs for controlsource and -binding
controlbinding: hide one unused typedef

This is not used internally.
baseparse: fix up name of default event vfuncs
baseparse: add vfuncs to intercept queries

Useful for video parses that want to attach matter or
find out if downstream supports certain metas.

API: GstBaseParseClass::src_query()
API: GstBaseParseClass::sink_query()

https://bugzilla.gnome.org/show_bug.cgi?id=691475
adapter: handle map failure
basesrc: handle map failure
typefind: handle map failure
docs: minor GstBaseParse docs fixes

Expose docs for gst_base_parse_finish_frame().
pipeline: add allow-none annotation for gst_pipeline_new()'s name property
po: update for new translated string
Use GST_*_1_0 environment variables everywhere

The _1_0 suffixed environment variables override the
non-suffixed ones, so if we're in an environment that
sets the _1_0 suffixed ones, such as jhbuild, we need
to set those to make sure ours actually always get
used.
Automatic update of common submodule

From 2a068ce to a942293
tests: disable ABI checks for architectures where the struct sizes are not up-to-date

https://bugzilla.gnome.org/show_bug.cgi?id=691828
docs: add a note to the gst_adapter_take_buffer() docs about buffer flags

https://bugzilla.gnome.org/show_bug.cgi?id=682110