defconfig: Switch to SLAB allocator
gcc: Fix compile errors for gcc 4.8

Use Linaro mainly because it compiles 40% faster than Google prebuilt.
Revert "msm: Make CONFIG_STRICT_MEMORY_RWX even stricter"

This reverts commit 5edf8295b89993bae69179fa9e9626fea00d90cf.

Thanks cyanogen for making me debug for a fucking full day! Thanks again.
Makefile: Do not use gcc-wrapper
defconfig: Compile with -O2 optimizations
defconfig: Enable xz compression
scripts: xz: Use smaller dictionary size
Makefile: Enable -Ofast optimizations