[Tcsh] tcsh-6.24.13 build issue on Solaris 11.4

[Nelson H. F. Beebe]

I have just built, validated, and installed tcsh-6.24.13 on 59
different systems in our test lab, and on our major servers.

I had to make one source code change for builds on Solaris 11.4 to
comment out the declaration and definition in tc.alloc.c of the
function malloc_usable_size() [starting at line 459], because it
conflicts with this system-wide declaration:

	% grep -n malloc_usable_size /usr/include/stdlib.h
	314:extern size_t malloc_usable_size(void *);

Once I did that, with #if 0 ... #endif wrappers, the build was
successful, but the tests all failed:

	./tests/testsuite[1470]: sed: not found [No such file or directory]
	./tests/testsuite[1470]: cat: not found [No such file or directory]
	./tests/testsuite[1515]: sed: not found [No such file or directory]
	....

I reran the tests with

	gmake SHELL=/bin/bash check

and then all tests passed:

	## ------------- ##
	## Test results. ##
	## ------------- ##

	196 tests were successful.
	53 tests were skipped.

-------------------------------------------------------------------------------
- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                                                          -
- Department of Mathematics, 110 LCB    Internet e-mail: beebe at math.utah.edu  -
- 155 S 1400 E RM 233                       beebe at acm.org  beebe at computer.org -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -
-------------------------------------------------------------------------------