mksymtab: Fix handling of final comma. Some C compilers can't handle them;...

mksymtab: Fix handling of final comma. Some C compilers can't handle them; Also add macro to provide the size of the symbol table

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5077 42af7a65-404d-4744-a932-0658087f49c3