configure: duplicate/incorrect order of -lrt

'-lrt' flag duplication/incorrect order
would cause 'undefined reference to clock_gettime' error during compilation time.

Before fix:
... -o qemu-bridge-helper qemu-bridge-helper.o    -lrt -pthread -lgthread-2.0 -lrt -lglib-2.0
After fix:
... -o qemu-bridge-helper qemu-bridge-helper.o    -pthread -lgthread-2.0 -lrt -lglib-2.0

Reference:
http://hi.baidu.com/sanitywolf/item/7a8b69c1e76dd220a0b50ab1

Signed-off-by: Rick Liu <yrliu.ca@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
configure: unset interfering variables

The check for big or little endianness relies on grep reporting
match/non-match on the generated binary. If the user specified
--binary-files=without-match in their GREP_OPTIONS, this will fail.

Let's follow what autoconf does and unset GREP_OPTIONS and CLICOLOR_FORCE
at the beginning of the script.

Reported-by: Eugene (jno) Dvurechenski <jno@linux.vnet.ibm.com>
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
rules.mak: Rewrite unnest-vars

The macro unnest-vars is the most important, complicated but hard to
track magic in QEMU's build system.

Rewrite it in a (hopefully) clearer way, with more comments, to make it
easier to understand and maintain.

Remove DSO_CFLAGS and module-objs-m that are not used.

A bonus fix of this version is, per object variables are properly
protected in save-objs and load-objs, before including sub-dir
Makefile.objs, just as nested variables are. So the occasional same
object name from different directory levels won't step on each other's
foot.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
rules.mak: remove .mo phony targets

Objects that come from multi-object modules are expanded already
in the -y variable when modules are disabled, and are a dependency
of the shared library.  They are only used to get libraries out of
multi-object modules.

If we add the libraries to each object like we do for cflags,
we do not need the .mo files at all except as an artificial
device in the Makefile.objs declarations.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>