Configure: fixed perl Makefile generation (ticket #334).

Dependancy tracking introduced in r5169 were not handled absolute path
names properly.  Absolute names might appear in CORE_DEPS if --with-openssl
or --with-pcre configure arguments are used to build OpenSSL/PCRE
libraries.

Additionally, revert part of r5169 to set NGX_INCS from Makefile
variables.  Makefile variables have $ngx_include_opt in them, which
might result in wrong include paths being used.  As a side effect,
this also restores build with --with-http_perl_module and --without-http
at the same time.

auto/lib/perl/make

@@ -31,7 +31,7 @@ $NGX_OBJS/src/http/modules/perl/Makefile: \\
 
 	cd $NGX_OBJS/src/http/modules/perl \\
 		&& NGX_PM_CFLAGS="\$(NGX_PM_CFLAGS) -g $NGX_CC_OPT" \\
-			NGX_INCS="\$(CORE_INCS) \$(HTTP_INCS)" \\
+			NGX_INCS="$CORE_INCS $NGX_OBJS $HTTP_INCS" \\
 			NGX_DEPS="\$(CORE_DEPS) \$(HTTP_DEPS)" \\
 		$NGX_PERL Makefile.PL \\
 			LIB=$NGX_PERL_MODULES \\

src/http/modules/perl/Makefile.PL

@@ -22,7 +22,7 @@ WriteMakefile(
 
     depend => {
         'nginx.c'     => join(" ", map {
-                             "../../../../../$_"
+                             m#^/# ? $_ : "../../../../../$_"
                          } (split(/\s+/, $ENV{NGX_DEPS}),
                             "src/http/modules/perl/ngx_http_perl_module.h"))
     },