chore, rename PKG_CHECK_VAR -> PKG_CHECK_VAR_MSG (to avoid naming conflict)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, extend PKG_CHECK_VAR_MSG functionality to match pkg-config's PKG_CHECK_VAR

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'bld/dist' into next

* bld/dist:
  minor, extend PKG_CHECK_VAR_MSG functionality to match pkg-config's PKG_CHECK_VAR
  chore, rename PKG_CHECK_VAR -> PKG_CHECK_VAR_MSG (to avoid naming conflict)
Merge branch 'next'

* next:
  minor, extend PKG_CHECK_VAR_MSG functionality to match pkg-config's PKG_CHECK_VAR
  chore, rename PKG_CHECK_VAR -> PKG_CHECK_VAR_MSG (to avoid naming conflict)