If the replacement table or function results in a value that isn't a
string or number (or nil), string.gsub raises an error. Have ustring
raise the same error.
Bug: T195326
Change-Id: Ic36f9f5d7adc0c14e7a4a94d3747335107acd8b6
Manually import LuaSandbox's git repository as a composer dependency to
provide the PHP stubs for phan.
Change-Id: I6226b9211f31d829da5a2775c6f5cf3599dd8ebc
normalization-data.lua is updated to Unicode 8.0.0 (libicu57).
charsets.lua is updated to match the character classes used by PCRE 8.35,
which seems to be Unicode 6.3.0.
upper.lua and lower.lua are still based on whatever ancient version of
Unicode is used by mb_strtoupper and mb_strtolower in HHVM 3.18.6.
Bug: T177498
Change-Id: I00b471176e1fd21123c22d187ff222928819e459
