tweak the illustration of latex figure environment
slight tweaks after #632
roxygenize for #632
make sure the output format is latex when we call render_latex()
no need to use do.call() -- just get the function from namespace and call it
I have an old bug here: knit2pdf() should be called when nosrc=TRUE (i.e. the text argument was not used), but I wrote !nosrc instead

it is safer to check is.null(outsrc) than nosrc=TRUE, so I did it, and reformatted the code a bit

besides, #632 is buggy: the variable out may not be created, so I moved it out of if () {}
tweak #622: the code can be as simple as this; no need to pass to engine_output()

I changed the option eval to echo
add the missing comma for #623
make the base url work for textile, i.e. opts_knit$get('base.url') #623
cosmetic changes
news for #623
export pat_textile()
roxygenize; closes #617 since #623 has done the job
bump version