x86: support salc,int1, fsetpm instructions. also added testcase suite/regress/x86_special_insn.py. see issue #58

Currently, =label is interpreted as a string instead of a symbol.

- x64_lea_label.py tests label addressing on x64 using all syntaxes (this
  demonstrates the incorrect addressing of labels on x64).
- x64_lea_label_rel.py tests rip relative label addressing on x64 using all
  available syntaxes (this demonstrates nasm syntax not being parsed).
- x64_lea_label_nasm_abs.py tests explicit absolute addressing on x64
  using nasm syntax (no equivalent exists in other syntaxes afaik).

Also adds x86 tests that check the same absolute addressing.

Refs: #28