The following, config line + make works fine under php v4.0.6, 

mcrypt Version 2.2.6

PHP Configure :
./configure --with-curl=/home/reserve/.usr --with-mcrypt=/home/reserve/.usr --with-zlib-dir=../zlib --with-png-dir=../libpng --with-gd=../gd-1.8.4 --with-jpeg-dir=/home/reserve/.usr --with-gettext --with-config-file-path=/home/reserve/.usr/etc/php410 --enable-track-vars --enable-force-cgi-redirect --enable-ftp

make

Build Error :

gcc -I. -I/usr/www/users/reserve/users/anders/.install/php-4.1.0/ext/mcrypt -I/usr/www/users/reserve/users/anders/.install/php-4.1.0/main -I/usr/www/users/reserve/users/anders/.install/php-4.1.0 -I/usr/www/users/reserve/users/anders/.install/php-4.1.0/Zend -I/home/reserve/.usr/include -I/usr/www/users/reserve/users/anders/.install/gd-1.8.4 -I/usr/local/include -I/usr/www/users/reserve/users/anders/.install/php-4.1.0/ext/mysql/libmysql -I/usr/www/users/reserve/users/anders/.install/php-4.1.0/ext/xml/expat  -I/usr/www/users/reserve/users/anders/.install/php-4.1.0/TSRM -g -O2  -c mcrypt.c && touch mcrypt.lo
mcrypt.c: In function `php_mcrypt_module_dtor':
mcrypt.c:253: syntax error before `td'
mcrypt.c:254: `td' undeclared (first use in this function)
mcrypt.c:254: (Each undeclared identifier is reported only once
mcrypt.c:254: for each function it appears in.)
*** Error code 1

Stop in /usr/www/users/reserve/users/anders/.install/php-4.1.0/ext/mcrypt.
*** Error code 1

Stop in /usr/www/users/reserve/users/anders/.install/php-4.1.0/ext/mcrypt.
*** Error code 1

Stop in /usr/www/users/reserve/users/anders/.install/php-4.1.0/ext.
*** Error code 1

Stop in /usr/www/users/reserve/users/anders/.install/php-4.1.0.