kbuild: sync with Linux Kernel v3.15-rc1

kbuild: sync with Linux Kernel v3.15-rc1

This commit imports Kbuild-related updates
from v3.14 to v3.15-rc1.

 - commit 3d3d6b8474204b6819688c9800774d52d370a538
    kbuild: LLVMLinux: Adapt warnings for compilation with clang
 - commit 61163efae02040f66a95c8ed17f4407951ba58fa
    kbuild: LLVMLinux: Add Kbuild support for building kernel with Clang
 - commit 79192ca8ebd9a25c583aa46024a250fef1e7766f
    scripts: objdiff: detect object code changes between two commits
 - commit 1c9e70a55b088d97a59241744fe459409d0c3582
    kbuild: create a build directory automatically for out-of-tree build
 - commit a03fcb50e816a69acffb13b5e56db75063aeba8a
    kbuild: remove redundant '.*.cmd' pattern from make distclean
 - commit 13338935f1574a2dcd1c891461b0dcc42f8cff42
    kbuild: move "quote" to Kbuild.include to be consistent
 - commit bfdfaeae500a3b194b73b01e92a8034791a58b7f
    kbuild: specify build_docproc as a phony target
 - commit f4d4ffc03efc864645b990e1d579bbe1b8e358a4
    kbuild: dtbs_install: new make target
 - commit 1e64ff42ea3d8d2fc8aa71f9717b3c1cb6c2f893
    Kbuild, lto: Disable LTO for asm-offsets.c
 - commit ccbef1674a1579842c7dbdf554efca85d2cd245a
    Kbuild, lto: add ld-version and ld-ifversion macros
 - commit ae63b2d7bdd9bd66b88843be0daf8e37d8f0b574
    scripts/tags.sh: Ignore *.mod.c
 - commit e36aaea28972c57a32a3ba5365e61633739719b9
    kbuild: Fix silent builds with make-4

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>