Change some dependency rules to make them work with MMS/MMK (VMS make utilities).

The VMS make utilities always need an action if they determine that a target is
older than a denpendency element.

Besides, rules like

some/header.h : some/source.c

some/source.c : some/file.dump
	$(PMC2CC) some/source.pmc

don't reflect the building process, as both the C and header file are generated
by the $(PMCCC) call.
[dynoplibs] Add a coth() op
[pmc] Added a coth() pmc method
[t] coth todo tests now pass
[imcc] Added coth to IMCC_subst_constants

Not 100% sure if this is required, but it seems like it is a good idea that
imcc knows about coth.
[dynoplibs] Added acot() op
[pmc] Added acot() pmc method
[t] Corrected acot() tests in trans-infan.t

The previously commented-out tests were not testing for the correct values.
The test results used here have been checked against expected values from
Mathematica.
[imcc] Added 'acot' to IMCC_subst_constants
[doc] Updated ChangeLog after coth() and acot() additions
[pmc] Documented the acot() and coth() methods
Merge pull request #965 from paultcochrane/ptc/add_coth_acot

Implement coth() and acot() math functions
[doc] Add POD for many Float PMC methods
[doc][ci skip] Tangent, not tan
[configure] handles architecture ARM v7
[configure] 'model name' is not present on all linux
[codingstd] String delimiter used with "split"
[GH #962] more cpu types (bsd, cygwin, solaris, win32, darwin)

Tested ok on cygwin, solaris, win32, darwin-x86 and darwin-ppc.
FWIW: Solaris on QEMU prints QEMU Virtual CPU version 1.1.2, different to the other VMs
/usr/bin/kstat -m cpu_info | grep implementation would print the parent CPU type:
x86 (GenuineIntel 623 family 6 model 2 step 3 clock 2793 MHz)
[codingstd] Fix cuddled else and missing semicolon
[ci skip][doc] Fix typo in tools path.