Pass ADAFLAGS to include.gpr and add CPPFLAGS to CFLAGS.

This patch does not apply the common style flags to include/*, it only
allow explicit user flags (ADAFLAGS) to override default flags.

The External is in shared.gpr so that there is only one environment
lookup for each variable.

Author: asarhaddon

include/include.gpr

@@ -64,6 +64,10 @@ library project Include is
          when others =>
             null;
       end case;
+
+      for Default_Switches ("Ada") use
+        Compiler'Default_Switches ("Ada")
+        & Shared.Adaflags;
    end Compiler;
 
    -------------

shared.gpr

@@ -90,6 +90,7 @@ abstract project Shared is
 
    Adaflags := External_As_List ("ADAFLAGS", " ");
    Cflags   := External_As_List ("CFLAGS", " ");
+   Cppflags := External_As_List ("CPPFLAGS", " ");
    Ldflags  := External_As_List ("LDFLAGS", " ");
 
    ---------
@@ -157,7 +158,7 @@ abstract project Shared is
       for Default_Switches ("Ada") use
         Compiler'Default_Switches ("Ada") & Adaflags;
       for Default_Switches ("C") use
-        Compiler'Default_Switches ("C") & Cflags;
+        Compiler'Default_Switches ("C") & Cflags & Cppflags;
 
    end Compiler;