New linter: Flawfinder (#1361)

* Flawfinder support added for C and C++

A minor modification to gcc handler was made to support flawfinder's
single-line output format that does not have a space following the
colon denoting the warning level.  gcc handler still passes its
Vader tests after this modification.

* Documentation fixes

* Revert documentation regression

* Added Flawfinder to table of contents

* Removed trailing whitespace

* Follow ALE conventions better

Added additional documentation and Vader tests

doc/ale-cpp.txt

@@ -153,6 +153,33 @@ g:ale_cpp_cpplint_options                           *g:ale_cpp_cpplint_options*
   This variable can be changed to modify flags given to cpplint.
 
 
+===============================================================================
+flawfinder                                                 *ale-cpp-flawfinder*
+
+g:ale_cpp_flawfinder_executable               *g:ale_cpp_flawfinder_executable*
+                                              *g:ale_cpp_flawfinder_executable*
+  Type: |String|
+  Default: `'flawfinder'`
+
+  This variable can be changed to use a different executable for flawfinder.
+
+
+g:ale_cpp_flawfinder_minlevel                   *g:ale_cpp_flawfinder_minlevel*
+                                                *b:ale_cpp_flawfinder_minlevel*
+  Type: |Number|
+  Default: `1`
+
+  This variable can be changed to ignore risks under the given risk threshold.
+
+
+g:ale_cpp_flawfinder_options                             *g:ale-cpp-flawfinder*
+                                                         *b:ale-cpp-flawfinder*
+  Type: |String|
+  Default: `''`
+
+  This variable can be used to pass extra options into the flawfinder command.
+
+
 ===============================================================================
 gcc                                                               *ale-cpp-gcc*