Add support for V: "v" (compiler) and "vfmt" fixer. (#3622)

* v: add "v fmt" fixer.

* v: add "v" (build) linter.

* v: fix vlint complaints and add documentation.

* v: add tests.

* v: use ale#Pad().

doc/ale-supported-languages-and-tools.txt

@@ -534,6 +534,9 @@ Notes:
   * `tslint`
   * `tsserver`
   * `typecheck`
+* V
+  * `v`
+  * `vfmt`
 * VALA
   * `uncrustify`
   * `vala_lint`!!

doc/ale-v.txt

@@ -0,0 +1,45 @@
+===============================================================================
+ALE V Integration                                               *ale-v-options*
+
+
+===============================================================================
+Integration Information
+
+`v` is V's build tool. `vfmt` (called as `v fmt` from the same
+executable that does the builds) is the autoformatter/fixer.
+
+g:ale_v_v_executable                                     *g:ale_v_v_executable*
+                                                         *b:ale_v_v_executable*
+
+  Type: |String|
+  Default: `'v'`
+
+  The executable that will be run for the `v` linter and the `vfmt` fixer.
+
+
+===============================================================================
+v                                                                     *ale-v-v*
+
+g:ale_v_v_options                                           *g:ale_v_v_options*
+                                                            *b:ale_v_v_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be set to pass additional options to the v linter.
+  They are injected directly after "v .".
+
+
+===============================================================================
+vfmt                                                               *ale-v-vfmt*
+
+g:ale_v_vfmt_options                                     *g:ale_v_vfmt_options*
+                                                         *b:ale_v_vfmt_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be set to pass additional options to the vfmt fixer.
+  They are injected directly after "v fmt".
+
+
+===============================================================================
+  vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:

doc/ale.txt

@@ -1593,6 +1593,7 @@ g:ale_linters                                                   *g:ale_linters*
   \   'text': [],
   \   'vue': ['eslint', 'vls'],
   \   'zsh': ['shell'],
+  \   'v': ['v'],
   \}
 <
   This option can be used to enable only a particular set of linters for a
@@ -3051,6 +3052,9 @@ documented in additional help files.
     tslint................................|ale-typescript-tslint|
     tsserver..............................|ale-typescript-tsserver|
     xo....................................|ale-typescript-xo|
+  v.......................................|ale-v-options|
+    v.....................................|ale-v-v|
+    vfmt..................................|ale-v-vfmt|
   vala....................................|ale-vala-options|
     uncrustify............................|ale-vala-uncrustify|
   verilog/systemverilog...................|ale-verilog-options|