core: add thread-safe strtok implementation (#3553)

This commit adds the support for a custom strtok implementation, which
is reentrant. On some systems strtok_r or strstep is available

core: add thread-safe strtok implementation (#3553)

This commit adds the support for a custom strtok implementation, which
is reentrant. On some systems strtok_r or strstep is available for that
purpose; however, since these are an extension, it is difficult to
control if it will be available on every supported system.

show more ...