Enable runtime cwrapper debugging; add tests

Enable runtime cwrapper debugging; add tests

* libltdl/config/ltmain.m4sh (func_emit_cwrapperexe_src):
Update comments. Initialize program_name. Eliminate _LENGTH
variables for string constants. In debug mode, print a
banner with known content before any other output. Remove
LTWRAPPER_DEBUGPRINTF macro. Add constants and variables
to support new --lt-debug option.
(func_emit_cwrapperexe_src:ltwrapper_debugprintf): Renamed to...
(func_emit_cwrapperexe_src:lt_debugprintf): this. Only print
messages if lt_debug != 0. Ensure appearance of messages
conforms to GCS.
(func_emit_cwrapperexe_src:lt_fatal): Ditto.
(func_emit_cwrapperexe_src:lt_error_core): Ditto.
(func_emit_cwrapperexe_src): Update all callers to lt_fatal.
Update all users of LTWRAPPER_DEBUGPRINTF (()) to call
lt_debugprintf () directly.
(func_emit_cwrapperexe_src:main): Consolidate option parsing.
Ensure first use of lt_debugprintf occurs after option parsing.
Add stanza to parse for --lt-debug and set lt_debug variable.
Use strcmp rather than strncmp, where safe.
* tests/cwrapper.at: Add new tests for --lt-debug and
-DLT_DEBUGWRAPPER.