GC stat after
==============
parsing:
        allocated_words: 37657442
        minor_words: 15582165
        promoted_words: 2166069
        major_words: 24241346
        minor_collections: 103
        major_collections: 24
        heap_words: 7015424
        heap_chunks: 20
        top_heap_words: 7015424
        compactions: 0
reformatting:
        allocated_words: 153497667
        minor_words: 131135436
        promoted_words: 36777601
        major_words: 59139832
        minor_collections: 553
        major_collections: 41
        heap_words: 9278464
        heap_chunks: 22
        top_heap_words: 9278464
        compactions: 0
GC stat before
==============
parsing:
        allocated_words: 41243812
        minor_words: 19168535
        promoted_words: 3911746
        major_words: 25987023
        minor_collections: 117
        major_collections: 25
        heap_words: 7015424
        heap_chunks: 20
        top_heap_words: 7015424
        compactions: 0
reformatting:
        allocated_words: 159464070
        minor_words: 137101839
        promoted_words: 39600932
        major_words: 61963163
        minor_collections: 576
        major_collections: 43
        heap_words: 8068096
        heap_chunks: 21
        top_heap_words: 8068096
        compactions: 0

GC stat after
=============
parsing:
        allocated_words: 35870858
        minor_words: 13795581
        promoted_words: 2141052
        major_words: 24216329
        minor_collections: 96
        major_collections: 24
        heap_words: 7015424
        heap_chunks: 20
        top_heap_words: 7015424
        compactions: 0
reformatting:
        allocated_words: 149597673
        minor_words: 127235442
        promoted_words: 36784443
        major_words: 59146674
        minor_collections: 539
        major_collections: 42
        heap_words: 395776
        heap_chunks: 1
        top_heap_words: 9278464
        compactions: 2

Replace a global buffer by a buffer local to parsing code.
This fixes a bug when processing multiple inputs. For instance with
refmt a.re b.re, b.re comments will (incorrectly) be read from a buffer
that begins with content from a.