Fix revlog-ng interaction with old-http. revlog.py wasn't trying to detect the version of a revlog file that doesn't exist on the filesystem (as is the case with old-http). Additionally, there was an off-by-one error in httprangereader.read (ranges in HTTP Range headers are inclusive), making it get more data than what was asked for. This made a struct.unpack complain that "unpack str size does not match format". Finally, with the two fixes above, test-static-http fails, since BaseHTTPServer doesn't understand ranges and returns too much data. Work around that by reading only the specified amount.

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A dir/b.o
? a.c
? a.o
? dir/c.o
? syntax
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abort: .hgignore: invalid pattern (relre): *.o
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A dir/b.o
? .hgignore
? a.c
? syntax
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.hgignore: ignoring invalid syntax 'invalid'
A dir/b.o
? .hgignore
? a.c
? a.o
? dir/c.o
? syntax
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A dir/b.o
? .hgignore
? a.c
? syntax
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A dir/b.o
? .hgignore
? a.c
? a.o
? dir/c.o
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A dir/b.o
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A b.o