modernize autoconf gsl.m4

[ferdymercury]

To avoid warnings when calling autoreconf, it would be beneficial to modernize https://github.com/ampl/gsl/blob/master/gsl.m4

by changing:

AC_TRY_RUN([program], [action-if-true], [action-if-false])
with
AC_RUN_IFELSE([AC_LANG_SOURCE([[program]])], [action-if-true], [action-if-false])

and

AC_TRY_LINK([includes], [function-body], [action-if-true], [action-if-false])
with
AC_LINK_IFELSE([AC_LANG_PROGRAM([[includes]], [[function-body]])], [action-if-true], [action-if-false])