Interpret argument in 'f ()' as nil instead of nothing

PR #3293 just checks for NoMethodError.

Safeguard against using MRB_INT64 with MRB_WORD_BOXING in 32-bit mode

Added documentation on function for globals

Fixed NaN boxing when MRB_INT16 is set

Fix incompatibility for Enumerable#first

Fix null pointer dereference in mrb_time_initialize

Fix typo in istruct.h

Reported by https://hackerone.com/raydot

Fix calling .arity on Proc with undefined `initialize`

Fix segfault on remove_method with invalid argument

Fix segfault when defining class inside instance_exec on primitive

Remove constant when a struct is redefined.

Get String length after args in String#chomp!

Read length after args in String#setbyte

Fix unsafe peephole optimization