### Allow hex and octal strings in dbPut and dbGet

It is now possible to convert hex and octal strings to integer fields
with `dbPut()`, `dbGet()` and related functions like the iocsh command
`dbpf` or through database links.

Possible incompatibility: Up to now, leading `0`s have been ignored,
now they switch to octal mode.

For backward compatibility, this behavior can be switched off, returning
to the old decimal only conversions, by setting the environment variable
`EPICS_DB_CONVERT_DECIMAL_ONLY` to anything except the empty string or
strings starting with `n`, `N`, `f`, `F` or `0` before `iocInit`.