Refactor: change "folder" to "directory" where needed.

This commit fixes every instance in which the word "folder" is
incorrectly used instead of "directory".

pages/common/cppcheck.md

@@ -3,13 +3,13 @@
 > A static analysis tool for C/C++ code.
 > Instead of syntax errors, it focuses on the types of bugs that compilers normally do not detect.
 
-- Recursively check the current folder, showing progress on the screen and logging error messages to a file:
+- Recursively check the current directory, showing progress on the screen and logging error messages to a file:
 
 `cppcheck . 2> cppcheck.log`
 
-- Recursively check a given folder, and don't print progress messages:
+- Recursively check a given directory, and don't print progress messages:
 
-`cppcheck --quiet {{path/to/folder}}`
+`cppcheck --quiet {{path/to/directory}}`
 
 - Check a given file, specifying which tests to perform (by default only errors are shown):
 
@@ -23,9 +23,9 @@
 
 `cppcheck --suppress={{test_id1}} --suppress={{test_id2}} {{path/to/file.cpp}}`
 
-- Check the current folder, providing paths for include files located outside it (e.g. external libraries):
+- Check the current directory, providing paths for include files located outside it (e.g. external libraries):
 
-`cppcheck -I {{include/folder_1}} -I {{include/folder_2}} .`
+`cppcheck -I {{include/directory_1}} -I {{include/directory_2}} .`
 
 - Check a Microsoft Visual Studio project (`*.vcxproj`) or solution (`*.sln`):