Fixes #4398: Move r31082, r31085 to v1.7 branch (MCA/base: document that is is)

---svn-pre-commit-ignore-below---

r31082 [[BR]]
Fix segmentation fault in handling of boolean variables in mca_base_var_set_value.

cmr=v1.7.5:reviewer=jsquyres

r31085 [[BR]]
MCA/base: document that is is valid for the string_value parameter to
an enumerator's mca_base_var_enum_sfv_fn_t can be NULL.

cmr=v1.7.5:ticket=#4398:reviewer=ompi-gk1.7
Fixes #4400: Move r31083 to v1.7 branch (Silence warning)

---svn-pre-commit-ignore-below---

r31083 [[BR]]
Silence warning

cmr=v1.7.5:reviewer=ompi-gk1.7


r31084 [[BR]]
Fully fix the PMI2 warning - turned out to be larger than originally thought due to the way the function was being handled across multiple files. Properly resolve the problem by not compiling the file if PMI2 is not desired, and then appropriately setting the visibility of the function within the module

Refs #4400
Fixes #4404: Move r31092 to v1.7 branch (Ensure that we send the)

---svn-pre-commit-ignore-below---

r31092 [[BR]]
Ensure that we send the specified signal to the entire process group of each member of the pid provided to us. This ensures that any children spawned by our children also see the signal

cmr=v1.7.5:reviewer=jsquyres


r31094 [[BR]]
Remove the job_control_forwarding logic as we want *any* signal to go to all members of the process group

Refs #4404
Fixes #4387: Move r31061 to v1.8 branch (Fix some set-but-not-used compiler warnings.)

---svn-pre-commit-ignore-below---

r31081 [[BR]]
coll/ml: fix a case not correctly handled by r31071

In r31071 I modified the logic to not increment the hierarchy level if
no processes were selected by that sbgp. That fixed a problem seen on
systems where we don't support process binding. The problem is there
is a case where we actually did select processes yet the number of
selected processes is 0. We need to increment the hierarchy in this case
as well.

This should fix the segmentation fault found by recent MTT runs. Once
this is committed to 1.7.5 remove the .ompi_ignore's from coll/ml and
bcol/ptpcoll. Tested with ompi-tests/ibm.

cmr=v1.7.5:reviewer=rhc