When --with-servlet and --with-gd, I got
gd.c: In function `php_if_imagepalettecopy':
gd.c:858: `gd_globals' undeclared (first use in this function)
gd.c:858: (Each undeclared identifier is reported only once
gd.c:858: for each function it appears in.)
gd.c: In function `php_if_imagepsloadfont':
gd.c:2122: `gd_globals' undeclared (first use in this function)
gd.c: In function `php_if_imagepsfreefont':
gd.c:2203: `gd_globals' undeclared (first use in this function)
gd.c: In function `php_if_imagepsencodefont':
gd.c:2229: `gd_globals' undeclared (first use in this function)
gd.c: In function `php_if_imagepsextendfont':
gd.c:2265: `gd_globals' undeclared (first use in this function)
gd.c: In function `php_if_imagepsslantfont':
gd.c:2291: `gd_globals' undeclared (first use in this function)
gd.c: In function `php_if_imagepstext':
gd.c:2366: `gd_globals' undeclared (first use in this function)
gd.c: In function `php_if_imagepsbbox':
gd.c:2504: `gd_globals' undeclared (first use in this function)
make[1]: *** [gd.lo] Error 1
make[1]: Leaving directory `/mnt/src/src/php-4.0.3pl1/ext/gd'
make: *** [all-recursive] Error 1

I guess --with-servlet cause #define ZTS 1 which in turns causes problem in gd.c