Fix autoconf xim tests.

The xim tests fail on systems where there is no X11 directory in the
default include path, such as FreeBSD, because X_CFLAGS is added to
CFLAGS and CFLAGS is not honored in C++. Fix the tests by adding
X_CFLAGS to CXXFLAGS.
Replace auto_ptr with estl::scoped_array.
Make new/delete compatible with C++11 and change new to use rxvt_malloc.
indent
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Remove optimization in refresh for cells containing a space.

The recent change introduced a regression and, while it can be fixed, it
is not worth the risk.