In ae0ceafb0c0d05cc80623b525070255e3abb34ef ruby_dtoa was switched to
use malloc instead of xmalloc, which means that consumers should be
using free instead of xfree. Otherwise we will artificially shrink
oldmalloc_increase_bytes.

Fixes this compiler warning:

    vsnprintf.c:1074:43: warning: 'uqval' may be used uninitialized in this function [-Wmaybe-uninitialized]

IA64 support was dropped in ticket #15894, so we can drop support for
HP-UX.

iff means if and only if, but readers without that knowledge might
assume this to be a spelling mistake. To me, this seems like
exclusionary language that is unnecessary. Simply using "if and only if"
instead should suffice.

```
In file included from sprintf.c:1256:
./vsnprintf.c:833:8: warning: adding 'int' to a string does not append to the string [-Wstring-plus-int]
                            IS_PRI_EXTRA_MARK(fmt)) {
                            ^~~~~~~~~~~~~~~~~~~~~~
./vsnprintf.c:826:34: note: expanded from macro 'IS_PRI_EXTRA_MARK'
           strncmp((s)+1, PRI_EXTRA_MARK+1, \
                          ~~~~~~~~~~~~~~^~
./vsnprintf.c:833:8: note: use array indexing to silence this warning
./vsnprintf.c:826:34: note: expanded from macro 'IS_PRI_EXTRA_MARK'
           strncmp((s)+1, PRI_EXTRA_MARK+1, \
                                        ^
1 warning generated.
```

Sanitizers report something inside of this function but it is
beyond my brain capacity.  Also the code is proven to work.
Let me ignore.

* cvt(): use signbit() instead of 1/d < 0
* w_float(): ditto
* ruby_float_step_size(): unit==0 check shall be prior to divisions
* arith_seq_float_step_size(): ditto
* rb_big_divide(): same as r65642
* fix_divide(): ditto
* rb_big_fdiv_double(): ditto
* fix_fdiv_double(): ditto


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65751 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

* vsnprintf.c (__sFILE): _lbfsize is not used.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58853 b2dd03c8-39d4-4d8f-98ff-823fe69b080e