[build] remove -Wdeclaration-after-statement

Declarations after statements has been permitted since C99.
(That was 20 years ago!)

configure.ac

@@ -1353,7 +1353,7 @@ AC_ARG_ENABLE([extra-warnings],
 )
 
 if test "$extrawarnings" = true || test "$extrawarnings" = error; then
-  TRY_CFLAGS([-g -O2 -g2 -Wall -Wmissing-declarations -Wdeclaration-after-statement -Wcast-align -Wsign-compare -Wnested-externs -Wpointer-arith -D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security])
+  TRY_CFLAGS([-g -O2 -g2 -Wall -Wmissing-declarations -Wcast-align -Wsign-compare -Wnested-externs -Wpointer-arith -D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security])
   TRY_LDFLAGS([-Wl,--as-needed])
   if test "$extrawarnings" = error; then
     AS_VAR_APPEND([CFLAGS], [" -Werror"])

meson_options.txt

@@ -121,7 +121,7 @@ option('build_extra_warnings',
 )
 option('warn_cflags',
 	type: 'string',
-	value: '-g -g2 -Wall -Wmissing-declarations -Wdeclaration-after-statement -Wcast-align -Wsign-compare -Wnested-externs -Wpointer-arith -D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security',
+	value: '-g -g2 -Wall -Wmissing-declarations -Wcast-align -Wsign-compare -Wnested-externs -Wpointer-arith -D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security',
 	description: 'CFLAGS to use when build_extra_warnings is active',
 )
 

src/CMakeLists.txt

@@ -41,7 +41,7 @@ if(CMAKE_C_COMPILER_ID MATCHES "GNU" OR CMAKE_C_COMPILER_ID MATCHES "Clang")
 	option(BUILD_EXTRA_WARNINGS "extra warnings")
 
 	if(BUILD_EXTRA_WARNINGS)
-		set(WARN_CFLAGS "-g -g2 -Wall -Wmissing-declarations -Wdeclaration-after-statement -Wcast-align -Wsign-compare -Wnested-externs -Wpointer-arith -D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security")
+		set(WARN_CFLAGS "-g -g2 -Wall -Wmissing-declarations -Wcast-align -Wsign-compare -Wnested-externs -Wpointer-arith -D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security")
 		set(WARN_LDFLAGS "-Wl,--as-needed")
 		# -Werror -Wbad-function-cast -Wmissing-prototypes
 	endif()