gallivm/llvmpipe: squash merge of the llvm-context branch

gallivm/llvmpipe: squash merge of the llvm-context branch

This branch defines a gallivm_state structure which contains the
LLVMBuilderRef, LLVMContextRef, etc.  All data structures built with
this object can be periodically freed during a "garbage collection"
operation.

The gallivm_state object has to be passed to most of the builder
functions where LLVMBuilderRef used to be used.

Conflicts:
	src/gallium/auxiliary/gallivm/lp_bld_tgsi_soa.c
	src/gallium/drivers/llvmpipe/lp_state_setup.c