Add helper functions to create allocations

Bug: 23535985

- Adds high-level helper functions such as rsCreateAllocation_char4 etc
  to the API.

- To accomplish this, adds "#RST_i" pattern replacement to the
  generator.  Similar to replacement of #1 with the equivalent parameter
  in the spec, the generator now replaces '#RST_i' patterns with the RS
  type equivalent of the parameter.  For e.g.:

"
...
t: i8, i16 # assume this is the first "replaceable" list in this spec
...
inline:
    rsCreateElement(RS_TYPE_#RST_1)
"

will generate
  - "rsCreateElement(RS_TYPE_SIGNED_8)" and
  - "rsCreateElement(RS_TYPE_SIGNED_16)"
respectively.

Change-Id: I162e3f3b9d89d477bf85e12dd300fd5b949dbd4b
3 files changed