devel/libstatgrab: update to 0.92.1

libstatgrab 0.92.1 [2021/07/27]

This release includes minor bugfixes and is API and ABI compatible with 0.92.
- Fix build with autoconf 2.70+.
- Fix CPU stats on older Linux kernels.
- Make sure to count processes in an unknown state.
- Check if -ltinfo is needed when linking ncurses.
- Fixes to build when cross-compiling.
- Fix build with -DNDEBUG.
- Handle vmmeter changes in FreeBSD 12.

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