Custom header files are missing when used in device.insert_code calls

[denisalevi]

Hi there,

I'm trying to run benchmarks on the newest releases of GeNN (4.5.1) and brian2GeNN (1.6) and wanted to use the insert_code mechanism which you used for the brian2geNN paper benchmarks (https://github.com/brian-team/brian2genn_benchmarks).

I used the <chrono> library for time point measurements, which I included via prefs.codegen.cpp.headers. This fails because the custom header is not included into model.cpp, which does includes code_lines blocks, which are filled via the insert_code mechanism.

This example reproduces the issue

from brian2 import *
import brian2genn

set_device('genn')

prefs.codegen.cpp.headers += ['<chrono>']
device.insert_code(
    "before_start", "std::chrono::high_resolution_clock::time_point _time_point;"
)

run(0*second)

I'll open a PR with a fix.

[denisalevi]

Closed with PR #132