Fix usage of MOD_* variables for MPM modules r1385216 broke building of mpm event with serf support. To fix, * introduce APACHE_MPMPATH_INIT/FINISH similar to APACHE_MODPATH_INIT/FINISH to create modules.mk and add MOD_* vars to it. * change APACHE_MPM_MODULE to only append to modules.mk, not overwrite * add APACHE_MPMPATH_INIT/FINISH to all MPMs

Change the configure-based MPM build mechanism to support building an MPM as a shared shared or dynamic module, primarily using the APACHE_MPM_MODULE() function. --enable-mpms-shared now builds/installs the MPMs as dynamic modules. (But no LoadModule directives are added.)

more configure-time support for dynamically loadable MPMs: . axe --with-mpm="shared" hack, replace with --enable-mpms-shared={all|list} . replace singular MPM_NAME with access to the list of enabled MPMs . replace singular MPM_SUBDIR with list MPM_SUBDIRS . enable OS/2 MPM in same manner as others with configure support instead of hard-coding in configure.in Current state: MPMs are built as static archives (but not linked to httpd) with --enable-mpms-shared, so they still have to be built with apxs to load dynamically.

Move logic to decide if an MPM is supported, and whether the MPM is threaded, down to the MPM itself. (server/mpm/FOO/config.m4, which runs before the actual MPM selection) server/mpm/config.m4 makes some general platform checks that can be used for MPM decisions, and contains some functions related to MPMs. XXX The check here for whether APR_POLLSET_THREADSAFE is available is a rough approximation and needs to be replaced by a run-time check. Replace the limited per-platform hard-coded MPM selection and the current defaulting to event (whether or not it works) with a selection based on which MPMs work on the platform, as reported by the MPMs themselves. (config2.m4, which runs after the MPMs record whether they are supported) Order of preference: WinNT (mingw32 only) then Event then Worker then Prefork