FFI with C: fix line offset in gcc error reports

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
docdown: read simple fence tag (type)

Signed-off-by: Jean Privat <jean@pryen.org>
src: nitunit and docdown use the fence-tag to skip non-nit code

Signed-off-by: Jean Privat <jean@pryen.org>
nitunit: enforce the testing of docunits (unless explicitely fence-tagged)

Signed-off-by: Jean Privat <jean@pryen.org>
man: explain docunits in man nitdoc

Signed-off-by: Jean Privat <jean@pryen.org>
nitdoc: increase the verbosity level for the numerous skip messages

Signed-off-by: Jean Privat <jean@pryen.org>
tests: test tagged fences for test_docdown and nitunit

Signed-off-by: Jean Privat <jean@pryen.org>
all: fix broken docunits

Signed-off-by: Jean Privat <jean@pryen.org>
all: fix broken markdown comments with missing or unwanted code blocks

Signed-off-by: Jean Privat <jean@pryen.org>
all: add `nitish` tag for code-blocks skipped by nitunit

Signed-off-by: Jean Privat <jean@pryen.org>
tests: niti skips tests with args for test_docdown and nitunit

Signed-off-by: Jean Privat <jean@pryen.org>
Merge: FFI with C: fix line offset in gcc error reports

Pull-Request: #944
Reviewed-by: Jean Privat <jean@pryen.org>
Merge: Use tagged-fences to discriminate docunits

Using heuristics to know what is a docunit and what is a raw block of code is not nice because syntax-errors in docunits happen and we do not want to silence them.

This PR introduces (and documents) the usage of tagged fences to force the programmer to explicit the role of the blocks of code.

By default (with indented block or untagged fences) code blocks are considered docunits to be checked by nitunit.
The tag `nit` does the same.
Any other tag cause docunit to ignore the whole block.

The special tag `nitish` makes docunit ignore the block but allows nitdoc to highlight it.

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Pull-Request: #941
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>