HHIR pass to do dead store elimination on frame locals

Summary: Does a liveness analysis and removes dead StLoc and StLocNT
instructions.  Also determines if stores are partially dead and tries to move
them to make them not dead.

Reviewed By: @swtaarrs

Differential Revision: D1639214
Remove an unused ir opcode, rename LdProp to LdContField

Reviewed By: @swtaarrs

Differential Revision: D1640044
Remove the various raw load/store instructions

Summary: Not very widely used now.  They also often don't really seem to save
significantly on boilerplate vs writing a small cg function these days (maybe
it originally did).  Also the func numparams thing was pretty bizarre to have
in these opcode (and was wrong in both arm and the emitStRaw implementation).

Reviewed By: @swtaarrs

Differential Revision: D1640078
Fix a bug in simpleCollectionOp that was throwing away array types

Summary: Only call ldRefReturn if we're going to do a LdRef on it.

Reviewed By: @swtaarrs

Differential Revision: D1640090

Signature: t1:1640090:1414504709:9590e3f0ca974b326c0f86b10e7057c88b085254
Reflow some paragraphs in type-system.{h,cpp}

Summary: @swtaarrs and@mxw made me change my fill column to 80 and now
shorter ones look weird.

Reviewed By: @edwinsmith

Differential Revision: D1641865

Signature: t1:1641865:1414449709:9fe81ba58bae065cef4fab0c71e32b808174141d