support ConstantVector, which can appear instead of ConstantDataVector when it contains an undef
emit I,F as signatures of vector types
SIMD fixes

Implement emscripten_float32x4_select, and prepare the UsedVars map in anticipation
of SIMD coercive calls which will need to know the full type.
Asm.js validation fixes for SIMD
Map vector load and store instructions to SIMD.js load and store APIs.
Merge pull request #50 from huningxin/incoming

Map vector load and store instructions to SIMD.js load and store APIs.
Optiomize InsertElement chains.

LLVM doesn't have vector constructor operators; instead it uses chains
of insertelements. Teach Emscripten to collect chains and detect when
they form splats and constructor calls so that it can emit the natural
API calls.
Reference the array buffer directly.

Instead of taking the array buffer from the typed array view, just
reference the buffer object directly.
Implement SIMD casts.

This uses the new single-argument SIMD constructor.
1.24.1
1.25.0