iij/mruby-io — pull request #35 by tmtm (2014-12-17 15:49:50+00:00)
Title: FIX: IO#read create a large number of objects.

same as #32 but don't use `String#<<`.

before:
```
% time ./bin/mruby -e 'File.open("/dev/zero").read(10000000); system "grep VmData /proc/#{$$}/status"'
VmData:	264168 kB
./bin/mruby -e 1.79s user 2.21s system 99% cpu 3.999 total
```
after:
```
% time ./bin/mruby -e 'File.open("/dev/zero").read(10000000); system "grep VmData /proc/#{$$}/status"'
VmData:	27264 kB
./bin/mruby -e 0.00s user 0.02s system 98% cpu 0.020 total
```