THTTPD: Remove use of lstat when directory indexing is enabled.  NuttX does not support symbolic links

Fix a few errors/warnings in THTTPD when indexing is enabled.  Still depends on non-existent lstat and ctime

Lincoln60: Add a thttpd-binfs configuration.  That configuration still does not work on initial commit

Damn.  THTTPD will not yet run with binfs because it wants an index.html file.  THTTPD does support indexing directories if CONFIG_THTTPD_GENERATE_INDICES=y, but there are some compilation issues that need to be fixed when that option is selected.

THTTPD: Add support for using binfs/ instead of NXFLAT.  NXFLAT is probably the better solution but recently compiler changes make it unusable.  binfs or ELF are fallback binary formats.  This commit adds an option to use binfs.

STM32 F4 Discovery: Move up_cxxinitialize from nuttx/configs/stm32f4discovery/src to apps/platform/stm32f4discovery where it belongs.

apps/examples/elf: Add configuration optionst o support building the hello++4 example that depends upon having uClibc++ available.  From Leo aloe3132.