Improve speed of SG_*IO debug functions

- SG_DEBUG & co are likely not enabled. Improve macros to test if
loglevel is above the to-be-shown level and only then call io code
- Note: This change requires that all SG_*IO functions no longer have a
trailing ";", e.g. SG_DEBUG("hi there...") is sufficient.
remove legacy whitespace in all SG_*IO functions

like SG_INFO( "foo") -> SG_INFO("foo")