configure: bump minimum AviSynth+ header version

AVISYNTH_INTERFACE_VERSION 10 fell in-between the releases of
3.7.2 and 3.7.3, and is required to be able to read the channel
layout information.

Signed-off-by: Stephen Hutchinson <qyot27@gmail.com>

configure

@@ -6656,8 +6656,8 @@ done
 
 # these are off by default, so fail if requested and not available
 enabled avisynth          && { require_headers "avisynth/avisynth_c.h avisynth/avs/version.h" &&
-                               { test_cpp_condition avisynth/avs/version.h "AVS_MAJOR_VER >= 3 && AVS_MINOR_VER >= 7 && AVS_BUGFIX_VER >= 1 || AVS_MAJOR_VER >= 3 && AVS_MINOR_VER > 7 || AVS_MAJOR_VER > 3" ||
-                                 die "ERROR: AviSynth+ header version must be >= 3.7.1"; } }
+                               { test_cpp_condition avisynth/avs/version.h "AVS_MAJOR_VER >= 3 && AVS_MINOR_VER >= 7 && AVS_BUGFIX_VER >= 3 || AVS_MAJOR_VER >= 3 && AVS_MINOR_VER > 7 || AVS_MAJOR_VER > 3" ||
+                                 die "ERROR: AviSynth+ header version must be >= 3.7.3"; } }
 enabled cuda_nvcc         && { check_nvcc cuda_nvcc || die "ERROR: failed checking for nvcc."; }
 enabled chromaprint       && { check_pkg_config chromaprint libchromaprint "chromaprint.h" chromaprint_get_version ||
                                require chromaprint chromaprint.h chromaprint_get_version -lchromaprint; }