options: move "-o threads=" help text to libfuse/

Parsing of and acting upon "-o threads" option is done in the bundled `libfuse/`,
so move the corresponding help text there too.
This make help text consistent with behavior
when building against system libfuse,
which doesn't support this option.

libfuse/lib/fuse.c

@@ -4432,6 +4432,9 @@ static void fuse_lib_help(void)
 "    -o intr                allow requests to be interrupted\n"
 "    -o intr_signal=NUM     signal to send on interrupt (%i)\n"
 "    -o modules=M1[:M2...]  names of modules to push onto filesystem stack\n"
+"    -o threads=NUM         number of worker threads. 0 = autodetect.\n"
+"                           Negative values autodetect then divide by\n"
+"                           absolute value. default = 0\n"
 "\n", FUSE_DEFAULT_INTR_SIGNAL);
 }
 

src/option_parser.cpp

@@ -299,9 +299,6 @@ usage(void)
     "    -o ignorepponrename=<bool>\n"
     "                           Ignore path preserving when performing renames\n"
     "                           and links. default = false\n"
-    "    -o threads=<int>       number of worker threads. 0 = autodetect.\n"
-    "                           Negative values autodetect then divide by\n"
-    "                           absolute value. default = 0\n"
             << std::endl;
 }