Configure: fixed make macros to use parentheses instead of braces.

Parentheses are more portable, in particular they are understood by nmake
while braces aren't.

auto/install

@@ -8,7 +8,7 @@ if [ $USE_PERL = YES ]; then
     cat << END                                                >> $NGX_MAKEFILE
 
 install_perl_modules:
-	cd $NGX_OBJS/src/http/modules/perl && \${MAKE} install
+	cd $NGX_OBJS/src/http/modules/perl && \$(MAKE) install
 END
 
     NGX_INSTALL_PERL_MODULES=install_perl_modules