"static const" instead of "#define" for script API M_* constants.

This makes referenced script API M_* constants visible in the debugger.

Modify rs lldb test for the constants so that it references them.

Adapted from https://android-review.googlesource.com/#/c/210789/

Test: aosp_arm64-eng on emulator
- run slang/tests, slang/lit-tests
- run rs lldb test suite
- run RsTest (32-bit, 64-bit)
- run cts -m RenderscriptTest (32-bit)
- confirmed that omitting type: or value: from constant: causes
  script_api/generate.sh to fail with an error

Change-Id: I9cc89771ad5d90432c0ea0a1885aae8d9003dafe
diff --git a/script_api/Generator.cpp b/script_api/Generator.cpp
index 456f214..f67e473 100644
--- a/script_api/Generator.cpp
+++ b/script_api/Generator.cpp
@@ -62,6 +62,7 @@
  * [version: ({Starting API level} [ {Last API level that supports this.}] | UNRELEASED)
  * [size: {32 or 64.  Used if this is available only for 32 or 64 bit code.}]
  * value: {The value of the constant.}
+ * type: {The type of the constant.}
  * [hidden:]   ...If present, don't document the constant.  Omit the following two fields.
  * [deprecated: [{Deprecation message.}]   ... This is deprecated.  Compiler will issue a wrning.
  * summary: {A one line string describing this section.}