Comments only, no change to functionality

If there were more than 6 integer arguments before the ellipsis, or
there were used more than 8 slots used until the ellipsis (e.g. by
a large intermediate struct) we generated wrong code.  See testcase.

This fixes two ABI testcases involving large arguments when there
are still registers available for later args.

* tccgen: re-allow long double constants for x87 cross
  sizeof (long double) may be 12 or 16 depending on host platform
  (i386/x86_64 on unix/windows).
  Except that it's 8 if the host is on windows and not gcc
  was used to compile tcc.

* win64: fix builtin_va_start after VT_REF removal
  See also a8b83ce43a95fa519dacfe7690a3a0098af7909c

* tcctest.c: remove outdated limitation for ll-bitfield test
  It always worked, there is no reason why it should not work
  in future.

* libtcc1.c: exclude long double conversion on ARM

* Makefile: remove CFLAGS from link recipes

* lib/Makefile: use target DEFINES as passed from main Makefile

* lib/armflush.c lib/va_list.c: factor out from libtcc1.c

* arm-gen.c: disable "depreciated" warnings for now

This reverts commit 4e04f67c94c97b4f28a4d73759a0ad38fb3a10f7. Requested by grischka.

    Jsut for testing. It works for me (don't break anything)
    Small fixes for x86_64-gen.c in "tccpp: fix issues, add tests"
    are dropped in flavor of this patch.

    Pip Cet:

    Okay, here's a first patch that fixes the problem (but I've found
    another bug, yet unfixed, in the process), though it's not
    particularly pretty code (I tried hard to keep the changes to the
    minimum necessary). If we decide to actually get rid of VT_QLONG and
    VT_QFLOAT (please, can we?), there are some further simplifications in
    tccgen.c that might offset some of the cost of this patch.

    The idea is that an integer is no longer enough to describe how an
    argument is stored in registers. There are a number of possibilities
    (none, integer register, two integer registers, float register, two
    float registers, integer register plus float register, float register
    plus integer register), and instead of enumerating them I've
    introduced a RegArgs type that stores the offsets for each of our
    registers (for the other architectures, it's simply an int specifying
    the number of registers). If someone strongly prefers an enum, we
    could do that instead, but I believe this is a place where keeping
    things general is worth it, because this way it should be doable to
    add SSE or AVX support.

    There is one line in the patch that looks suspicious:

             } else {
                 addr = (addr + align - 1) & -align;
                 param_addr = addr;
                 addr += size;
    -            sse_param_index += reg_count;
             }
             break;

    However, this actually fixes one half of a bug we have when calling a
    function with eight double arguments "interrupted" by a two-double
    structure after the seventh double argument:

    f(double,double,double,double,double,double,double,struct { double
    x,y; },double);

    In this case, the last argument should be passed in %xmm7. This patch
    fixes the problem in gfunc_prolog, but not the corresponding problem
    in gfunc_call, which I'll try tackling next.

* fix some macro expansion issues
* add some pp tests in tests/pp
* improved tcc -E output for better diff'ability
* remove -dD feature (quirky code, exotic feature,
  didn't work well)

Based partially on ideas / researches from PipCet

Some issues remain with VA_ARGS macros (if used in a
rather tricky way).

Also, to keep it simple, the pp doesn't automtically
add any extra spaces to separate tokens which otherwise
would form wrong tokens if re-read from tcc -E output
(such as '+' '=')  GCC does that, other compilers don't.

 * cleanups
  - #line 01 "file" / # 01 "file" processing
  - #pragma comment(lib,"foo")
  - tcc -E: forward some pragmas to output (pack, comment(lib))
  - fix macro parameter list parsing mess from
    a3fc54345949535524d01319e1ca6378b7c2c201
    a715d7143d9d17da17e67fec6af1c01409a71a31
    (some coffee might help, next time ;)
  - introduce TOK_PPSTR - to have character constants as
    written in the file (similar to TOK_PPNUM)
  - allow '\' appear in macros
  - new functions begin/end_macro to:
      - fix switching macro levels during expansion
      - allow unget_tok to unget more than one tok
  - slight speedup by using bitflags in isidnum_table

Also:
  - x86_64.c : fix decl after statements
  - i386-gen,c : fix a vstack leak with VLA on windows
  - configure/Makefile : build on windows (MSYS) was broken
  - tcc_warning: fflush stderr to keep output order (win32)

The old code assumed that if an argument doesn't fit into the available
registers, none of the subsequent arguments do, either. But that's
wrong: passing 7 doubles, then a two-double struct, then another double
should generate code that passes the 9th argument in the 8th register
and the two-double struct on the stack. We now do so.

However, this patch does not yet fix the function calling code to do the
right thing in the same case.