fixes issue #1547

Currently fails directwrite backend.

hb-directwrite.cc: In constructor 'TextAnalysis::TextAnalysis(const wchar_t*, uint32_t, const wchar_t*, DWRITE_READING_DIRECTION)':
hb-directwrite.cc:489:18: error: 'TextAnalysis::mText' will be initialized after [-Werror=reorder]
   const wchar_t* mText;
                  ^~~~~
hb-directwrite.cc:488:12: error:   'uint32_t TextAnalysis::mTextLength' [-Werror=reorder]
   uint32_t mTextLength;
            ^~~~~~~~~~~
hb-directwrite.cc:282:3: error:   when initialized here [-Werror=reorder]
   TextAnalysis (const wchar_t* text, uint32_t textLength,
   ^~~~~~~~~~~~
hb-directwrite.cc: In function 'hb_bool_t _hb_directwrite_shape_full(hb_shape_plan_t*, hb_font_t*, hb_buffer_t*, const hb_feature_t*, unsigned int, float)':

../src/hb-machinery.hh: In instantiation of 'const Type& StructAtOffset(const void*, unsigned int) [with Type = unsigned int]':
../src/hb-font.cc:144:85:   required from here
../src/hb-machinery.hh:63:12: error: cast from 'const char*' to 'const unsigned int*' increases required alignment of target type [-Werror=cast-align]
 { return * reinterpret_cast<const Type*> ((const char *) P + offset); }
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/hb-machinery.hh: In instantiation of 'Type& StructAtOffset(void*, unsigned int) [with Type = unsigned int]':
../src/hb-font.cc:145:79:   required from here
../src/hb-machinery.hh:66:12: error: cast from 'char*' to 'unsigned int*' increases required alignment of target type [-Werror=cast-align]
 { return * reinterpret_cast<Type*> ((char *) P + offset); }
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/hb-machinery.hh: In instantiation of 'Type& StructAtOffset(void*, unsigned int) [with Type = int]':

https://github.com/harfbuzz/harfbuzz/issues/1546

Try at fixing https://github.com/harfbuzz/harfbuzz/issues/1546

clang -Weverything still left to be ported to pragmas

hb-machinery.hh:111:37: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]

Also ignore -Wtype-limits.

Third try to fix access. Followup 6879efc2

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=12532
Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=922303

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=12532
Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=922303

Better fix for 480406cd
This way we behave the same on 32bit and 64bit archs.

Rewrote struct FDSelect3_4.ranges as ArrayOf
Updated FDSelect3_4::sanitize () to call ranges.sanitize ()
nRanges now a function to return a reference to ranges.len