configure: Update libmysofa check with a new symbol.

The current code in libavfilter/af_sofalizer.c requires
mysofa_neighborhood_init_withstepdefine function, which only appeared
in libmysofa 0.7. Use this function in configure script to bail out
early if a too old libmysofa is found in the system instead of failing
at compile time.

configure

@@ -6239,8 +6239,8 @@ enabled libmfx            && { check_pkg_config libmfx libmfx "mfx/mfxvideo.h" M
                                { require libmfx "mfx/mfxvideo.h" MFXInit "-llibmfx $advapi32_extralibs" && warn "using libmfx without pkg-config"; } }
 enabled libmodplug        && require_pkg_config libmodplug libmodplug libmodplug/modplug.h ModPlug_Load
 enabled libmp3lame        && require "libmp3lame >= 3.98.3" lame/lame.h lame_set_VBR_quality -lmp3lame $libm_extralibs
-enabled libmysofa         && { check_pkg_config libmysofa libmysofa mysofa.h mysofa_load ||
-                               require libmysofa mysofa.h mysofa_load -lmysofa $zlib_extralibs; }
+enabled libmysofa         && { check_pkg_config libmysofa libmysofa mysofa.h mysofa_neighborhood_init_withstepdefine ||
+                               require libmysofa mysofa.h mysofa_neighborhood_init_withstepdefine -lmysofa $zlib_extralibs; }
 enabled libnpp            && { check_lib libnpp npp.h nppGetLibVersion -lnppig -lnppicc -lnppc -lnppidei ||
                                check_lib libnpp npp.h nppGetLibVersion -lnppi -lnppc -lnppidei ||
                                die "ERROR: libnpp not found"; }