Description:
------------
May have to reinstall Apache on a Slackware installation in order to configure PHP.

Basically, even if i just do a ./configure --with-apache it wont find the apache path. 

Apache is running fine, the configure complains about not being able to locate the file http.d in /usr/local/apache/

Reproduce..

Reproduce code:
---------------
Ok.. so i do the following

root@xxx:/home/xxx/php-5.1.2#locate httpd.h

/var/www/htdocs/manual/programs/httpd.html.ja.jis
/var/www/htdocs/manual/programs/httpd.html.html
/var/www/htdocs/manual/programs/httpd.html.en
/var/www/htdocs/php/manual_en/install.fhttpd.html
/var/www/htdocs/php/manual_en/install.omnihttpd.html
/var/www/htdocs/php/manual_en/install.otherhttpd.html
/var/www/htdocs/php/manual_en/install.unix.fhttpd.html
/var/www/htdocs/php/manual_en/install.windows.omnihttpd.html
/usr/src/linux-2.4.31/include/config/khttpd.h
/usr/include/apache/httpd.h  <-- * here *

So, i try ./configure --with-apache=/usr/include/apache/



Expected result:
----------------
I expected it to compile. Maybe i am making a beginners mistake, as i havent been using linux for very long, but i have searched on Google already for answers, to no avail.


Actual result:
--------------
root@xxx:/home/xxx/php-5.1.2# ./configure --with-apache=/usr/include/apache/
loading cache ./config.cache
checking for Cygwin environment... no
checking for mingw32 environment... no
checking for egrep... grep -E
checking for a sed that does not truncate output... /usr/bin/sed
checking host system type... i686-pc-linux-gnu
checking target system type... i686-pc-linux-gnu
checking for gcc... gcc
checking whether the C compiler (gcc  ) works... yes
checking whether the C compiler (gcc  ) is a cross-compiler... no
checking whether we are using GNU C... yes
checking whether gcc accepts -g... yes
checking whether gcc and cc understand -c and -o together... yes
checking how to run the C preprocessor... gcc -E
checking for AIX... no
checking whether ln -s works... yes
checking if compiler supports -R... no
checking if compiler supports -Wl,-rpath,... yes
checking for re2c... no
configure: warning: You will need re2c 0.9.11 or later if you want to regenerate PHP parsers.
checking for gawk... gawk
checking for bison... bison -y
checking for bison version... 1.35 (ok)
checking for flex... flex
checking for yywrap in -lfl... yes
checking lex output file root... lex.yy
checking whether yytext is a pointer... yes
checking for working const... yes
checking for flex version... 2.5.4 (ok)
checking whether to force non-PIC code in shared modules... yes
checking for pthreads_cflags... -pthread
checking for pthreads_lib...

Configuring SAPI modules
checking for AOLserver support... no
checking for Apache 1.x module support via DSO through APXS... no
checking for Apache 1.x module support... no
configure: error: Invalid Apache directory - unable to find httpd.h under /usr/include/apache/