[PATCH] OS/2 patches for master branch, try 2

Hi/2.

These are OS/2 patches for master branch. Patches for 1.4 branch are
reflected.

[PATCH 1/5] configury: support DLLs on OS/2
[PATCH 2/5] m4: support to load modules on OS/2
[PATCH 3/5] configury: append $EXEEXT suffix to the executable,
[PATCH 4/5] configury: add -Zargs-resp to LDFLAGS on OS/2.
[PATCH 5/5] esyscmd: fdopen() with a text mode explicitly on OS/2.