Fix memleaks found with AddressSanitizer/LeakSanitizer

Found with:
ASAN_OPTIONS="detect_odr_violation=1,strip_path_prefix=$(pwd)/" build/sdrangel

Fixes:
Direct leak of 176096 byte(s) in 5503 object(s) allocated from:
    #0 0x7f3a464f46c8 in operator new(unsigned long) ../../../../src/libsanitizer/asan/asan_new_delete.cpp:95
    #1 0x7f3a44009219 in Airline::Init::Init() sdrbase/util/airlines.cpp:5559
    #2 0x7f3a43dc797d in _sub_I_65535_0.0 (build/lib/libsdrbase.so+0x3c797d) (BuildId: fb568b705538a6e506ee23027626f4366b25aa50)
    #3 0x7f3a46c6ce3d in call_init elf/dl-init.c:74
    #4 0x7f3a46c6ce3d in call_init elf/dl-init.c:26

sdrbase/util/airlines.cpp

@@ -5560,3 +5560,8 @@ Airline::Init::Init()
         s += 4;
     }
 }
+
+Airline::Init::~Init()
+{
+    qDeleteAll(m_icaoHash);
+}

sdrbase/util/airlines.h

@@ -55,6 +55,7 @@ private:
     friend struct Init;
     struct Init {
         Init();
+        ~Init();
         static const char *m_airlines[];
     };
     static Init m_init;