Improve syntax and semantic check calls from GUI

Shortcuts are available on the GUI to trigger the syntax and both the syntax and semantic checks of the C/C++ compiler without building the project.

• Currently, the check is executed on every project resource (i.e. on files and directories) that is selected in the Package Explorer view. However, this also means that the check is executed on files too that are not understandable for the compiler, i.e. the bin directory with dependency and C/C++ source files, and other generated files. So the check should be restricted to file types that are accepted by the compiler.

• In addition, the flags of the compiler are not taken into account when executing these checks from the GUI. Therefore, even if the compiler flag for e.g. OOP are turned on, the compiler mistreats the class and other OOP specific keywords.

• Disable check syntax/semantic check buttons when a Java project item is selected