Describe the bug
A clear and concise description of what the bug is.

When building my own 3d viewer in open3d which uses filament for rendering i observed that setting indirect lighting by loading *_ibl.ktx file faild with inability to load spherical harmonics from *_ibl.ktx file. The file contains proper 3 x 9 table for spherical harmonics.

After investigation i figured that the reason for this locals sensitivity is the std::strtof function used on line ilament/libs/image/src/KtxBundle.cpp:298 of current master branch to parse the spherical harmonics list. See also std::strtof reference.

To Reproduce
Steps to reproduce the behavior:

1. set system locals to for example de_DE or de_UTF8

2. run your program which uses indirect lighting only

3. surfaces will be black only

4. Open editor (eg vi/vim)

5. replace all . in spherical harmonics list (key sh) with ,

6. rerun demo

7. Surface colors will be back

Expected behavior
A clear and concise description of what you expected to happen.

That KtxBundle::getSphericalHarmonics returns valid spherical harmonics list independent of which locals are set on the system filament or filament based library is used.

Screenshots
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std::strtof failing on eg.: German locale

with , as decimal separator eg: in German locale

Logs
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use screenshots of logs, copy them as text.

Desktop (please complete the following information):

• OS: [e.g. iOS] Mint 20 i386
• GPU: [e.g. NVIDIA GTX 1080] irrelevant
• Backend: [OpenGL/Vulkan] guess opengl through intel/open3d python wheel

Smartphone (please complete the following information):

• Device: [e.g. Pixel 2]
• OS: [e.g. Android Pie 9.0]

Additional context
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