Double quotes inside multiline strings fail to parse

[arshajii]

This works:

'''
'a'
'''

This fails:

'''
"a"
'''

with error

Uncaught exception:

  (Scanf.Scan_failure
   "scanf: bad input at char number 3: end of input not found")

Raised at file "scanf.ml" (inlined), line 444, characters 18-40
Called from file "scanf.ml", line 1164, characters 4-75
Called from file "seqaml/lexer.mll", line 52, characters 25-33
Called from file "grammar.ml", line 23209, characters 15-27
Called from file "grammar.ml", line 23236, characters 24-51
Called from file "seqaml/codegen.ml", line 17, characters 14-56
Called from file "runner.ml", line 15, characters 12-77
Called from file "runner.ml", line 32, characters 4-28
Called from file "runner.ml", line 61, characters 19-43