Toward version 3.7.5.1.  This check-in updates the version number and also
patches the pager so that it never spills cache while in WAL mode.  The
latter patch fixes ticket [2d1a5c67dfc23] and also prevents excessive WAL
file sizes if the pager cache starts thrashing.  A few test cases fail.

FossilOrigin-Name: 2e5a912ad781f7554c718df6340c809472f87022

• VERSION[diff]
• configure[diff]
• manifest[diff]
• manifest.uuid[diff]
• src/pager.c[diff]
• test/walcrash2.test[diff]
• tool/shell1.test[diff]