Revert "extras/strpack: Use statically linked libLLVM symbols"

This reverts commit f4bbb30f2849c461bbcf93f8ca00fd85e747d6e4.

Conflicts:

	deps/Rmath
Revert "Expose libLLVM symbols"

This reverts commit 40ca7a05bc50ea1e640bce2539955281ff794b54.

Conflicts:

	deps/Rmath
	src/julia.expmap
Merge branch 'topic/unlibllvm'

Re-hides the symbols from libLLVM. Undoes #1991. Closes #2180.