patch 8.2.0849: BeOS code is not maintained and probably unused

Problem:    BeOS code is not maintained and probably unused.
Solution:   Remove the BeOS code. (Emir Sari, closes #5817)
diff --git a/src/Makefile b/src/Makefile
index c4bce68..e8f84465 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2026,7 +2026,7 @@
 RSRC_DIR = os_mac_rsrc
 
 PRO_MANUAL = os_amiga.pro os_win32.pro \
-	os_mswin.pro winclip.pro os_beos.pro os_vms.pro $(PERL_PRO)
+	os_mswin.pro winclip.pro os_vms.pro $(PERL_PRO)
 
 # Default target is making the executable and tools
 all: $(VIMTARGET) $(TOOLS) languages $(GUI_BUNDLE)
@@ -2193,10 +2193,6 @@
 	$(CPROTO) -DWIN32 -UHAVE_CONFIG_H $< > proto/$@
 	echo "/* vim: set ft=c : */" >> proto/$@
 
-os_beos.pro: os_beos.c
-	$(CPROTO) -D__BEOS__ -UHAVE_CONFIG_H $< > proto/$@
-	echo "/* vim: set ft=c : */" >> proto/$@
-
 os_vms.pro: os_vms.c
 # must use os_vms_conf.h for auto/config.h
 	mv auto/config.h auto/config.h.save
@@ -3394,9 +3390,6 @@
 objects/optionstr.o: optionstr.c
 	$(CCC_NF) $(LUA_CFLAGS) $(PERL_CFLAGS) $(PYTHON_CFLAGS) $(PYTHON3_CFLAGS) $(RUBY_CFLAGS) $(TCL_CFLAGS) $(ALL_CFLAGS) -o $@ optionstr.c
 
-objects/os_beos.o: os_beos.c
-	$(CCC) -o $@ os_beos.c
-
 objects/os_qnx.o: os_qnx.c
 	$(CCC) -o $@ os_qnx.c