Draft: libvlc: don't inherit variable on config parameters

var_InheritBool() reads the value from the config when a parameter is not passed explicitly. We don't want to involve the config file when ignoring or resetting the config.

For example setting "ignore-config" in a config file will make it impossible to use "reset-config" to fix it.

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v2:

• draft as it sits on top of !2393 (merged)
• added more volatile variables that can only be read from the libvlc_int_t and not from the config file