configure: Also create tests/api

This should fix some problems on some fate clients like openbsd
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -6014,6 +6014,7 @@ enabled getenv || echo "#define getenv(x) NULL" >> $TMPH
 
 mkdir -p doc
 mkdir -p tests
+mkdir -p tests/api
 echo "@c auto-generated by configure" > doc/config.texi
 
 print_config ARCH_   "$config_files" $ARCH_LIST