Maintainer mode should be enabled in development branches.

Also adds helpful commenting.

Add bin/switch_maint_mode
Disable maintainer mode for release.
Fix incomplete merge for stub functions in H5Fdhdfs.c

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Add solaris 64bit alignment issue to "Known Problems".

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…10.13 and 10.14.

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* Reverts lock/unlock callback signature to 1.8.21 version

This callback is unused in 1.8. The ros3 and hdfs VFDs are the only VFDs
that have the lock callback implemented and that is just as no-op stubs.
These stubs were removed so the callbacks are now NULL pointers, like
the other VFDs in 1.8.

* Trivial whitespace fix

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…#270) (#277)

* Cache the pointer to the next point to process after the last call to
H5S__get_select_elem_pointlist.  This allows the normal process of
iterating over the points in batches to be much more efficient, as the
library does not need to traverse the entirety of the preceding points
every time the funciton is re-entered.

* Update RELEASE.txt for point selection iteration performance fix.

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add check_version workaround for binary compatibility to "Known
Problems".