Free obsolete memtables outside the dbmutex had a memory leak.

Summary:
The commit at 27bbef11802d27c80df7e0b27091876df23b9986 had a memory leak
that was detected by valgrind. The memtable that has a refcount decrement
in MemTableList::InstallMemtableFlushResults was not freed.

Test Plan: valgrind ./db_test --leak-check=full

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14391
Removed redundant slice_transform.h and memtablerep.h

Summary:
Removed redundant slice_transform.h and memtablerep.h

Test Plan:
make check

Reviewers:

CC:

Task ID: #

Blame Rev:
Fix build without glibc

Summary: The preprocessor does not follow normal rules of && evaluation, tries to evaluate __GLIBC_PREREQ(2, 12) even though the defined() check fails.  This breaks the build if __GLIBC_PREREQ is absent.

Test Plan: Try adding #undef __GLIBC_PREREQ above the offending line, build no longer breaks

Reviewed By: igor

Blame Rev: 4c81383628db46d35b674000a3668b5a9a2498a6
Memtables should be deleted appropriately in the unit test.

Summary:
Memtables should be deleted appropriately in the unit test.

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:
Cleaning up INSTALL.md -- there were two occurrences of gflags
Removing reference to doc/impl.html
Clarify CompactionFilter thread safety requirements

Summary: Documenting our discussion

Test Plan: make

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: igor

Differential Revision: https://reviews.facebook.net/D14403
Merge branch 'master' into wiredtiger