Revert "disable awk dotts pipe in SunOS, fix #2173"

This reverts commit b952bf7d20bdc31c0f243981cb754e7fa7b9460c.
fix --trace problem with __rvm_date, update #2174, update #2175
fix deleting default alias
Merge remote-tracking branch 'upstream/master'
Call __rvm_detect_system right after declaration