Having multiple benchmarks for a single name is something specific to
the gotest output, so grouping benchmarks by name is not something that
belongs in the junit package.
This function was used in the past to perform some operations on the
individual output lines before joining them together. However, now it's
only used to combine the collection of lines into a single output
string.
Whitespace prefix of output lines was carried over from the old v1
version, but in some cases it removes too much whitespace. Ideally it
would detect the common prefix of all output lines for a given text and
only trim that. Until that's fixed, let's just stop removing the
whitespace.
Fixes#131
