Catch missing imports and errors like #1520 and #1521
__E901,E999,F821,F822,F823__ are the "_showstopper_" [flake8](http://flake8.pycqa.org) issues that can halt the runtime with a SyntaxError, NameError, etc. Most other flake8 issues are merely "style violations" -- useful for readability but they do not effect runtime safety.
* F821: undefined name `name`
* F822: undefined name `name` in `__all__`
* F823: local variable name referenced before assignment
* E901: SyntaxError or IndentationError
* E999: SyntaxError -- failed to compile a file into an Abstract Syntax Tree
* 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.
* add fd index checks to subr subsetter
also added oss-fuzz test case
* undid SubrSubsetParam::is_valid
because already validated by SubrClosures.valid
It is not visually noticeable but apparently affected by kern format2 correct implementation.
I should've checked CoreText result which can't as CircleCI outage.