#622 mapwindow.c: remove log_calls() debug artifact (backtrace/execinfo)

[Allen D Byrne]

The GTK3V2MAIN-specific file app/bin/mapwindow.c contains a debug-only function log_calls() (lines 95-117) that uses backtrace() and backtrace_symbols() from <execinfo.h> to print call-stack information to the log. It is guarded with #ifndef WIN32 and is called from MapRedraw() and MapChangeScale().</execinfo.h>

This appears to be a development artifact introduced during GTK3 porting work. It is not present in the default branch.

The function should be removed before GTK3V2MAIN is merged upstream:

• execinfo.h / backtrace() is not available on all POSIX platforms (notably musl libc / Alpine Linux)
• It adds overhead on every map redraw and scale change even when logging is disabled
• The call-stack information duplicates what a debugger or a standard LOG() call already provides

Fix: remove log_calls(), the #include <stdio.h> / #include <execinfo.h> block at lines 92-93, and the two call sites in MapRedraw() (~line 258) and MapChangeScale() (~line 349).</execinfo.h></stdio.h>