ext/gd: use --with instead of --enable

By convention it probably makes sense to stick with this even when
dropping the *-dir=DIR part.

Fix the travis script, which is either way using the wrong version, with
*-dir

See:
php#3632 (comment)
https://autotools.io/autoconf/arguments.html

Author: eli-schwartz

ext/gd/config.m4

@@ -30,8 +30,8 @@ fi
 PHP_ARG_WITH(xpm-dir, for the location of libXpm,
 [  --with-xpm-dir[=DIR]      GD: Set the path to libXpm install prefix], no, no)
 
-PHP_ARG_ENABLE(freetype, for FreeType 2,
-[  --enable-freetype       GD: Enable FreeType 2 support], no, no)
+PHP_ARG_WITH(freetype, for FreeType 2,
+[  --with-freetype         GD: Enable FreeType 2 support], no, no)
 
 PHP_ARG_ENABLE(gd-jis-conv, whether to enable JIS-mapped Japanese font support in GD,
 [  --enable-gd-jis-conv    GD: Enable JIS-mapped Japanese font support], no, no)

travis/compile.sh

@@ -70,7 +70,7 @@ $TS \
 --with-pspell=/usr \
 --with-enchant=/usr \
 --enable-wddx \
---enable-freetype \
+--with-freetype \
 --with-xpm-dir=/usr \
 --with-kerberos \
 --enable-sysvmsg \