CRAN errors with release 3.0.0

[Jean-Romain]

• clang-UBSAN probably coming from ✔️

https://github.com/Jean-Romain/lidR/blob/6cbf2aea3c73144d5347d1a8136aae4dd39ad6f4/tests/testthat/test-lascheck.R#L9

• quantization test failing on 32 bit solaris. Preprocessor must check for SunOS

https://github.com/Jean-Romain/lidR/blob/6cbf2aea3c73144d5347d1a8136aae4dd39ad6f4/src/RcppFunction.cpp#L236

• Incorrect number of trees with fedora clang. I don't know why

 ── 1. Failure: lastrees supports a LAScatalog (@test-lastrees.R#175) ──────────
     length(na.omit(unique(las@data$treeID))) not equal to 274.
     1/1 mismatches
     [1] 272 - 274 == -2

• sf error reproducible on travisCI only ✔️

 ── 1. Error: lasmergespatial works with sf (@test-lasmergespatial.R#37) ───────
     st_crs(x) == st_crs(y) is not TRUE