remove assert() from AsmToken::getStringContents()

bindings/nodejs/consts/keystone.js

bindings/python/keystone/keystone_const.py

bindings/ruby/keystone_gem/lib/keystone/keystone_const.rb

include/keystone/keystone.h

llvm/include/llvm/MC/MCParser/MCAsmLexer.h

llvm/lib/MC/MCParser/AsmParser.cpp

llvm/lib/MC/MCParser/COFFAsmParser.cpp

llvm/lib/MC/MCParser/ELFAsmParser.cpp

llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp