* src/hb-cff-interp-dict-common.hh: Use ull for unsigned int64_t
The llu suffix does not work for older Visual Studio versions
(pre-2013), but ull works for all the compilers that we attempt to
support.
* test/api: Fix build on pre-C99 compilers
Ensure variables are declared at the top of the block.
* src/hb-dsalgs.hh: Add specialization for hb_is_signed<> for __int8
Pre-Visual Studio 2010 does not consider __int8 (which is typedef'ed to
int8_t) to be equivilant to signed char, so the compiler cannot find the
corresponding hb_is_signed<> specialization that is needed.
The interesting thing is unsigned __int8 is considered to be equivilant
to unsigned char, so as the other types (short, int, long) that we look
for here, so only the specialization for __int8 is added here.
This will fix builds on Visual Studio 2008 at least.
