Added hb-ot-cff1-table.cc to hb-subset sources
Deleted unused variable (charset)

fixed misc Charset bugs
added source file hb-ot-cff1.table.cc
renamed things for clarity & consistency

Templatized ArgStack so it may store the default value along with blend deltas as BlendArg while parsing blend operator arguments in CFF2 charstring
Added get_region_count() method to VarRegionList & VariationStore

renamed confusing Stack.size to Stack.count

Factored out CFF1 & CFF2 common subsetting code in hb-subset-cff-common.hh

Subr-flattened charstrings are temporarily re-encoded in ByteStrBuff during "plan" phase, then copied to hb_serialize_context_t during "write" phase

CSOpSet may callback opcode processing "virtual" functions via CRTP

Numer struct may store a value as fixed optionally in addition to int and float

along with CFF2 charstring interpreter
factored out common code between CFF1 & CFF2 to CSInterpreter
moved fetch_op from Interpreter to InterpEnv
misc code clean up & bug fixes

along with HB_OT_TAG_cff1

"CFF" is used for shared structs & sources between CFF1 & CFF2
except OT:cff is for CFF version 1 table

Unreferenced subroutines are nullified (not removed) in a subset font

Separate Interpreter struct from hb-ot-cff-common-private.hh in a set of four header files, augmented for CharString (CS):
hb-cff-interp-common-private.hh
hb-cff-interp-dict-common-private.hh
hb-cff-interp-cs-common-private.hh
hb-cff-interp-cs.hh

Interpreter runtime is separated off as a new struct InterpEnv sub-classed differently for Dict and CharString (CS)

It was bloating a multi-FD subset font unnecessarily
defined a wrapper struct FDMap for fdmap

Added sources hb-ot-cff-table.hh, hb-subset-cff.cc & hh
Templatized Index because CFF uses 16-bit count while CFF2 uses 32-bit
Misc code cleanup & bug fixes