kvutils: fix __KVU_FUNCTION on non-glibc enviroments
kvutils: fix __KVU_FUNCTION on non-glibc enviroments

Fix build errors that occured if __GNUC_PREREQ was not defined
(old glibc or other libc implementations). Affects for instance
cygwin builds.

Bug was reported by Al Oomens on ecasound-list (2010/Mar).

jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2