patch 8.2.0320: no Haiku support

Problem:    No Haiku support.
Solution:   Add support for Haiku. (Emir Sari, closes #5605)

Filelist

@@ -599,6 +599,14 @@ SRC_AMI =	\
 		src/testdir/amiga.vim \
 		src/xxd/Make_amiga.mak \
 
+# source files for Haiku (also in the extra archive)
+SRC_HAIKU =	\
+		src/os_haiku.h \
+		src/os_haiku.rdef \
+		src/gui_haiku.cc \
+		src/gui_haiku.h \
+		src/proto/gui_haiku.pro \
+
 # source files for the Mac (also in the extra archive)
 SRC_MAC =	\
 		src/INSTALLmac.txt \
@@ -634,13 +642,13 @@ SRC_QNX =	\
 		src/proto/gui_photon.pro \
 		src/proto/os_qnx.pro \
 
-
 # source files for the extra archive (all sources that are not for Unix)
 SRC_EXTRA =	\
 		$(SRC_AMI) \
 		$(SRC_AMI_DOS) \
 		$(SRC_DOS) \
 		$(SRC_DOS_BIN) \
+		$(SRC_HAIKU) \
 		$(SRC_MAC) \
 		$(SRC_QNX) \
 		$(SRC_VMS) \