mesa,llvm,meson: Update llvm to 8.0.1 plus define and use LLVM version globally

- Add missing dependency on libedit
- Define LLVMVERSION on the same lines as GCCVERSION and other tools
- Use LLVMVERSION in mesa and meson.bbclass to get llvm version instead of
  hardcoding it
- Use llvm patches unmodified from meta-clang, helps in keeping them in
  sync
- Define PREFERRED_VERSION for llvm, llvm-native, nativesdk-llvm

(From OE-Core rev: 3c08b638348abd543fc92baf56c28ca16ae6aac6)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-graphics/mesa/mesa.inc

@@ -36,6 +36,10 @@ PLATFORMS ??= "${@bb.utils.filter('PACKAGECONFIG', 'x11 wayland', d)} \
 
 export YOCTO_ALTERNATE_EXE_PATH = "${STAGING_LIBDIR}/llvm${MESA_LLVM_RELEASE}/llvm-config"
 export YOCTO_ALTERNATE_MULTILIB_NAME = "${base_libdir}"
+export LLVM_CONFIG = "${STAGING_BINDIR_NATIVE}/llvm-config${MESA_LLVM_RELEASE}"
+export WANT_LLVM_RELEASE = "${MESA_LLVM_RELEASE}"
+
+MESA_LLVM_RELEASE ?= "${LLVMVERSION}"
 
 EXTRA_OEMESON = " \
     -Dshared-glapi=true \
@@ -107,10 +111,8 @@ GALLIUMDRIVERS_append = "${@bb.utils.contains('PACKAGECONFIG', 'r600', ',r600',
 GALLIUMDRIVERS_append = ",virgl"
 
 PACKAGECONFIG[gallium] = "-Dgallium-drivers=${GALLIUMDRIVERS}, -Dgallium-drivers=''"
-MESA_LLVM_RELEASE ?= "8.0.0"
 PACKAGECONFIG[gallium-llvm] = "-Dllvm=true -Dshared-llvm=true, -Dllvm=false, llvm${MESA_LLVM_RELEASE} llvm-native \
                                ${@'elfutils' if ${GALLIUMDRIVERS_LLVM33_ENABLED} else ''}"
-export WANT_LLVM_RELEASE = "${MESA_LLVM_RELEASE}"
 PACKAGECONFIG[xa]  = "-Dgallium-xa=true, -Dgallium-xa=false"
 
 PACKAGECONFIG[lima] = ""