Improve kdevelop searching for separate src and build folders

When loading a new project if the source path contains '/src/'
check to see if there is an existing directory in a seperate build folder.

This makes using kdevelop with kdesrc-build defaults work better

REVIEW: 115464
Code cleanup after parent commit
Fix inspecting of nested STL containers.

The problem is that GDB MI shows no children for dynamic STL objects,
it just add "dynamic" attribute to it. Here is -var-list-children
output for std::map< int, std::vector<std::string> > object:

SEND: "-var-list-children --thread 1 --frame 0 --all-values "var1" 0 5
kdevelop(20230)/kdevelop (gdb debugger) GDBDebugger::GDB::processLine:
GDB output:
"^done,numchild="2",displayhint="map",children=[child={name="var1.[0]",
exp="[0]",numchild="0",value="0",type="const int",thread-id="1"},
child={name="var1.[1]",exp="[1]",numchild="0",value="{...}",
type="std::vector<std::basic_string<char, std::char_traits<char>,
 std::allocator<char> >, std::allocator<std::basic_string<char,
std::char_traits<char>, std::allocator<char> >
> >",thread-id="1",displayhint="array",dynamic="1"}],has_more="0""

As you see, the second variable, std::vector<std::string> has
numchild="0", but dynamic="1". This patch adds extra check for
"dynamic" attribute in variables.

BUG: 330734