Enable AC_USE_SYSTEM_EXTENSIONS to avoid implicit function declarations
Brought to you by:
chulbe2lsu,
t-beu
Use AC_USE_SYSTEM_EXTENSIONS to enable declarations of asprintf,
vasprintf in the glibc headers. Otherwise the corresponding configure
probes will fail with compilers that do not support implicit function
declarations by default.
Related to:
Thanks for the patch. Merged by https://github.com/tbeu/matio/commit/66ba48751a4bbf91070ca9680d0d65237ceb3872 (and later mirrored to SF).