C compiler

This is the 'Level 7' compiler as described in _T_h_e_ _C_ _P_r_o_g_r_a_m_m_i_n_g_ _L_a_n_g_u_a_g_e
(Kernighan & Ritchie).

Output must be processed by the UNIX assembler 'as'. Undefine the preprocessor
variable 'unix' to produce a version compatible with the Interdata CAL
assembler.

The 16-bit version (produced by defining the preprocessor variable HALFW) is
only partially implemented -- 'static', 'long' and 'float' don't work.

Jobjar:
	- fix alignment of aggregates (currently all structs and unions are on
	  a word boundary)
	- implement double-precision (currently 'double' is synonymous with
	  'float') and unsigned short
	- complete 16-bit version
