* configure.in:
Add checks for vasprintf, localtime_r.
* gdate.c (g_date_set_time):
Use localtime if localtime_r is not available.
* gstrfuncs.c (g_strdup_vprintf):
Use glibc vasprintf if possible; it's a bit faster than using
GLib routines, and makes output code a bit smaller.
* acconfig.h:
Remove HAVE_VSNPRINTF and HAVE_VPRINTF. autoheader picks these
up automatically and puts them in config.h.in.