user: move common-user includes to a subdirectory of {bsd,linux}-user/

Avoid polluting the compilation of common-user/ with local include files;
making an include file available to common-user/ should be a deliberate
decision in order to keep a clear interface that can be used by both
bsd-user/ and linux-user/.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

bsd-user/meson.build

@@ -4,7 +4,7 @@ endif
 
 bsd_user_ss = ss.source_set()
 
-common_user_inc += include_directories('.')
+common_user_inc += include_directories('include')
 
 bsd_user_ss.add(files(
   'bsdload.c',

linux-user/meson.build

@@ -4,8 +4,8 @@ endif
 
 linux_user_ss = ss.source_set()
 
-common_user_inc += include_directories('host/' / host_arch)
-common_user_inc += include_directories('.')
+common_user_inc += include_directories('include/host/' / host_arch)
+common_user_inc += include_directories('include')
 
 linux_user_ss.add(files(
   'elfload.c',