Fix building mono with icc

When compiling mono with icc (ICC) 14.0.0 20130728 the build fails on

  CC     libmonoruntimesgen_la-sgen-stw.lo

with the following error:

Assembler messages:
Error: suffix or operands invalid for `lea'

Apparently icc (or the assembler) dislikes the rip-based LEA
operation. This can be worked around by manually assembling the
instruction and replacing it with the corresponding byte sequence.

This change is released under the MIT license.
Merge pull request #1044 from ranma42/fix-icc-build

Fix building mono with icc