* Add debugging info about so size to build output
This adds a small python script to tools that captures before-and-after
.so sizes between builds and outputs this in the build output via a
string such as:
------ pybind11_tests.cpython-35m-x86_64-linux-gnu.so file size: 924696 (decrease of 73680 bytes = 7.38%)
------ pybind11_tests.cpython-35m-x86_64-linux-gnu.so file size: 998376 (increase of 73680 bytes = 7.97%)
------ pybind11_tests.cpython-35m-x86_64-linux-gnu.so file size: 998376 (no change)
Or, if there was no .so during the build, just the .so size by itself:
------ pybind11_tests.cpython-35m-x86_64-linux-gnu.so file size: 998376
This allows you to, for example, build, checkout a different branch,
rebuild, and easily see exactly the change in the pybind11_tests.so
size.
It also allows looking at the travis and appveyor build logs to get an
idea of .so/.dll sizes across different build systems.
* Minor libsize.py script changes
- Use RAII open
- Remove unused libsize=-1
- Report change as [+-]xyz bytes = [+-]a.bc%
