Fix: winsize/sidebarpos restored incorrectly

[faimerth]

This PR mitigated the following bugs related to msgwin/sidebar/wingeom setup:

• Issue geany cannot restore previous window size (reopen after maximized) #1593. It is meaningless to save maximized window's size. Now geany "can restore to window sizeA" after unmaximizing.
• Right sidebar's position will be incorrectly restored with "save winsize/pos" unchecked or "msgwin right" checked.
  The former is because gtk_widget_get_allocated_width(pane) get '1' at startup.
  src/ui_utils.c: void ui_swap_sidebar_pos(void):
gtk_paned_set_position(GTK_PANED(pane), gtk_widget_get_allocated_width(pane) - gtk_paned_get_position(GTK_PANED(pane)));
  The later is because sidebar position's setup is prior to msgwin's setup. If msgwin is too wide, sidebar's position will get inside the msgwin.
• Potential Fault: "Preference->change msgwin orientations->Apply". Because config file saved before the ui update, the wrong position but the correct orientation of msgwin will be recorded. If crash happened before gently exiting, geany will show wrong layout at next start. Hence the ui update of main window should be prior to config file saving.

Test with:
Ubuntu 16.04,
Geany 1.36 (1046ea4) ---- with configuration (msgwin bottom/right, sidebar left/right, (un)save winpos/size),
GTK 3.18.9.

[codebrainz]

I only had a quick glance at the code, no comment about the purpose of the PR, but more of a note for future cleanup/merging. You should follow the Geany code style (documented in HACKING and found in neighboring code), stuff like putting spaces between operators and operands. Also you shouldn't leave pointless stuff like if (1) branches.