cppcheck: Expr is always false because 'else if' cond matches previous cond

add a vexl prefix entry for movdqu to fix issue #85

Update ud_opcode.py to also support Python 3.x

No UD_ATTRIBUTE_PACKED for ud_mnemonic_code

Enable silent rules

Expose the offset of the modrm byte

Fix standalone compilation

Add entries in optable.xml for obsolete 8087 instructions FNENI (DB E0), FNDISI (DB E1), FNSETPM (DB E4), and FRSTPM (DB E5).  All but the latter execute (as NOPs) on modern CPUs.

cppcheck: Expression is always false because 'else if' condition matches previous condition at line 158

I don't think packing the enum into 16-bit is advantageous in any way, also it doesn't happen on MSVC, for which the macro is defined to be empty. The ud struct's size shouldn't change (at least it doesn't on Clang/GCC for 64-bit), only the offset of the mnemonic member would be aligned to 4 bytes.

Hit this on Arch, which uses Python 3 as default interpreter. The scripts should either call `/usr/bin/python2` instead of just `/usr/bin/python` or this script must be updated. The proposed change(s) in particular:

    * `dict.iteritems()` has been replaced by `dict.items()`, which returns a lazy view instead. `itemslist()` resolves this.

udint.h needs to include types.h in order to get the __UD_STANDALONE__
macro. Otherwise it will think we're in non-standalone mode and fail to
compile in standalone mode.

tests: use bash instead of sh to run difftest.sh

Fix duplicate <opr> for sqrtss

On Ubuntu, /bin/sh is a symlink to /bin/dash, however difftest.sh uses
bash-specific constructs and fails when run using dash. Therefore, run
this script explicitly using bash.

Commit 88bb68bb added avx instructions
but forgot to remove the old <opr> information for the sqrtss
instruction. Let's get rid of it.

Operand size symbolic constants aren't really enumerations. Use the
preprocessor instead of enum to represent them. (Issue #66)

(Issue #62) In __UD_STANDALONE__ mode, the onus is now on the client to
make sure that the right set of files are included prior to including
udis86.h in their environment. types.h no longer assumes the
availability of header files. I haven't tried this myself in a kernel
build environment, but I'm hoping someone will, and get back with
problems if any.

This fixes issue #65, and also included are minor updates to some
test operand cases.

Some changes for loading the lib dynamically under Windows

* added dllexport modifiers for MSVC compilation
* included extern.h from within decode.c to expose its symbols
* deleted ud_insn_sext_imm as it isn't referenced anywhere

Defines are required for uint16_t etc., size_t, and va_list in case of
__UD_STANDALONE on linux.  The stddef.h and stdarg.h defines would
otherwise come from stdio.h were it included.

This avoids overriding ${docdir} as given at the command line so it
won't be inconsistent in a few Makefiles.