Added docgen documentation
Fixes two minor typos.
Reformats text to fit width of 80 columns.
Adds docgen to list of documentation to build.
Adds some cross references to docgen manual.
Transforms docgen sample to be generated from source.
command syntax is allowed in expressions
updated grammar.txt
fix the segfault in #827
parser support anon iterators
Merge branch 'devel' of https://github.com/Araq/Nimrod into devel
next steps for closure iterators
nest PreMain inside NimMain for easier consumption of static libraries developed in Nimrod

fixes many uses of $N instead of $n for new lines that don't affect #line directives
fix the error "only proc headers can feature pragmas" when compiling in JS mode
closure iterators almost work
closure iterators work
small code cleanups
Merge branch 'devel' of https://github.com/Araq/Nimrod into devel
typeClasses now documented in grammar.txt
renderer knows about nkStaticTy and nkTypeClassTy