pmaports.cfg: bump version to 3 (!222)

This version has the "crossdirect" package, which will be required for
the new pmbootstrap code that uses the crossdirect compilation method by
default.

pmaports.cfg

@@ -2,7 +2,7 @@
 # Version numbers (for sanity checks in pmbootstrap)
 # - "version" gets compared with "pmb.config.pmaports_min_version"
 # - "pmbootstrap_min_version" gets compared with "pmb.config.version"
-version=2
+version=3
 pmbootstrap_min_version=1.5.1
 branch_pmos=master
 # Compatible branch from Alpine's aports repository