JSON import: accept fractional mtime values

For sub-second precision, if we ever want to add that.

src/dir_import.c

@@ -465,6 +465,12 @@ static int iteminfo(void) {
       C(rint64(&iv, UINT64_MAX));
       ctx->buf_dir->flags |= FF_EXT;
       ctx->buf_ext->mtime = iv;
+      // Accept decimal numbers, but discard the fractional part because our data model doesn't support it.
+      if(*ctx->buf == '.') {
+          con(1);
+          while(*ctx->buf >= '0' && *ctx->buf <= '9')
+              con(1);
+      }
     } else if(strcmp(ctx->val, "hlnkc") == 0) {      /* hlnkc */
       if(*ctx->buf == 't') {
         C(rlit("true", 4));