Remove some compile warnings.
Remove some compile warnings in the vhdlpp code
vhdlpp: Minor code cleaning.
vhdlpp: Added basic support for concatenated expressions.
vhdlpp: Emit '-' std_logic value as 'x'.

Note: It is not a direct ("don't care" vs "unknown"), but I could not
find anything that suits better.
vhdlpp: Fix error message for 'right attribute.
vhdlpp: Emit use_types in Architecture.
vhdlpp: Support for integer() function.

Note: I could not find any info about the integer() function, but it is
used in the VHDL standard packages (e.g. math_real, see:
http://www.csee.umbc.edu/portal/help/VHDL/packages/mathpack.vhd)
Real numbers are rounded, this is compatible with ModelSim behavior.
Fix the modpath edge and vpi_put_delay() code

The code to get the correct modpath delay for a given edge had the X and Z
entries swapped.

When putting a delay from the VPI the 2 delay to twelve delay mapping was
incorrect and the to/from X delays were also not being calculated correctly.
Add support for putting three and six delays from the VPI
Merge pull request #47 from orsonmmz/concat

Expression concatenation in VHDL
Add support for putting a single delay from the VPI
Fix a reference to an undefined element.
lexor handles arbitrary length defines in the precompiled_defiles file.
[spqr] Dealing with noop stmts

Noops shouldn't affect anything, and therefore are just an empty case statment.
Merge branch 'master' into spqr