Link the EGL library with Mesa. SDL's `GL_GetProcAddress` now calls
`eglGetProcAddress` rather than lookup procedures directly in the Mesa
library.
Components may still wish to list 'mesa_api' in LIBS to access OpenGL
headers.
Fix#2711
This is a follow-up commit to "Increase default warning level", which
overrides Genode's new default warning level for targets contained in
higher-level repositories. By explicitly whitelisting all those targets,
we can selectively adjust them to the new strictness over time - by
looking out for 'CC_CXX_WARN_STRICT' in the target description files.
Issue #465