This separates the 32-bit sysv/linux/bsd code from the 64-bit linux

code, and makes it possible to link code compiled with different
options to those used to compile libffi.  For example, a
-mlong-double-128 libffi can be used with -mlong-double-64 code.

Using the return value area as a place to pass parameters wasn't such
a good idea, causing a failure of cls_ulonglong.c.  I didn't see this
when running the mainline gcc libffi testsuite because that version of
the test is inferior to the upstreamm libffi test.

Using NUM_FPR_ARG_REGISTERS rather than NUM_FPR_ARG_REGISTERS64 meant
that a parameter save area could be allocated before it was strictly
necessary.  Wrong but harmless.  Found when splitting apart ffi.c
into 32-bit and 64-bit support.

man/Makefile.in

@@ -187,6 +187,7 @@ FFI_EXEC_TRAMPOLINE_TABLE = @FFI_EXEC_TRAMPOLINE_TABLE@
 FGREP = @FGREP@
 GREP = @GREP@
 HAVE_LONG_DOUBLE = @HAVE_LONG_DOUBLE@
+HAVE_LONG_DOUBLE_VARIANT = @HAVE_LONG_DOUBLE_VARIANT@
 INSTALL = @INSTALL@
 INSTALL_DATA = @INSTALL_DATA@
 INSTALL_PROGRAM = @INSTALL_PROGRAM@