Recognize the special string "NULL" to indicate no entry point
should be called for the library.  Equivalent to leaving the
field empty.

Use (int) with %d conversions for portability

Adds a "install_custom.cmake" hook that can be put into a CPU-specific
subdirectory under the "defs" directory, that can perform extra
installation steps as required for the project/mission.

Tweaks the "add_cfe_tables" function such that it can also be called from
the install_custom.cmake script to generate additional/alternative table
binary files for that CPU.

The main update is that it uses the "APP_NAME" parameter to associate
the table files with the app library, so the same set of include files
can be used.  This relies on the target-scope properties being used.
Historically that string wasn't verified, it could have been any unique
string, but now it should match the app if this is to work as expected.

Changing the implementation return types to CFE_Status_t
to match the function prototypes.

Fix #1522, add printf format casts

Fix #1505, accept "NULL" as entry point

Fix #1538, add capability to generate multiple tables

For a table build where the app name passed to cfe_add_tables
does not match the actual app name, it must use the
APP_DYNAMIC_TARGET_LIST and APP_STATIC_TARGET_LIST variables
to get the target list for installation.

Fix #1474, #1552, Resolve API prototype/implementation discrepancies