remove GCC_WARN

Now, the only usage of GCC_WARN is for the guard of PRINTF_F in wincurs.h.
This guard can be removed safely, as PRINTF_F is already used unconditionally in extern.h.

sys/unix/hints/include/compiler.370

@@ -133,10 +133,6 @@ CCXXFLAGS+=-Wno-deprecated-declarations
 endif  # WANT_WIN_QT
 endif  # clang-specific ends here
 
-# enable some optional code in various NetHack source files
-CFLAGS+=-DGCC_WARN
-CCXXFLAGS+=-DGCC_WARN
-
 ifdef MAKEFILE_SRC
 ifdef WANT_WIN_QT
 # when switching from Qt5 to Qt6 or vice versa, any old .moc files will be

sys/unix/hints/include/cross-pre.370

@@ -159,8 +159,7 @@ MSDOS_TARGET_CFLAGS = -c -O -I../include -I../sys/msdos -I../win/share \
         -Wall -Wextra -Wno-missing-field-initializers -Wreturn-type -Wunused \
         -Wformat -Wswitch -Wshadow -Wwrite-strings \
 	-Wimplicit -Wimplicit-function-declaration -Wimplicit-int \
-	-Wmissing-parameter-type -Wold-style-definition -Wstrict-prototypes \
-	-DGCC_WARN
+	-Wmissing-parameter-type -Wold-style-definition -Wstrict-prototypes
 PDCINCL += -I$(PDCPORT)
 PDC_TARGET_CFLAGS = $(MSDOS_TARGET_CFLAGS) -Wno-unused-parameter \
 			-Wno-missing-prototypes
@@ -285,7 +284,6 @@ WASM_CFLAGS += -Wshadow
 WASM_CFLAGS += $(WINCFLAGS)   #WINCFLAGS set from multiw-2.370
 WASM_CFLAGS += -DSYSCF -DSYSCF_FILE=\"/sysconf\" -DSECURE
 WASM_CFLAGS += -g -I../include -DNOTPARMDECL
-WASM_CFLAGS += -DGCC_WARN
 # NetHack sources control
 WASM_CFLAGS += -DDLB
 WASM_CFLAGS += -DHACKDIR=\"$(HACKDIR)\"