pmgen: Move passes out of pmgen folder

- Techlib pmgens are now in relevant techlibs/*.
- `peepopt` pmgens are now in passes/opt.
- `test_pmgen` is still in passes/pmgen.
- Update `Makefile.inc` and `.gitignore` file(s) to match new `*_pm.h` location,
  as well as the `#include`s.
- Change default `%_pm.h` make target to `techlibs/%_pm.h` and move it to the
  top level Makefile.
- Update pmgen target to use `$(notdir $*)` (where `$*` is the part of the file
  name that matched the '%' in the target) instead of `$(subst _pm.h,,$(notdir
  $@))`.

techlibs/ice40/ice40_wrapcarry.pmg

@@ -0,0 +1,15 @@
+pattern ice40_wrapcarry
+
+match carry
+	select carry->type.in(\SB_CARRY)
+endmatch
+
+match lut
+	select lut->type.in(\SB_LUT4)
+	index <SigSpec> port(lut, \I1) === port(carry, \I0)
+	index <SigSpec> port(lut, \I2) === port(carry, \I1)
+endmatch
+
+code
+	accept;
+endcode