Added note to cbuildcap and reserved cs1 == 0 (#103)

This should close #94 .

Author: francislaus

Diff for: src/insns/cbuildcap_32bit.adoc

@@ -24,8 +24,11 @@ sealed, `cs1` 's permissions and bounds are equal or a superset of `cs2` 's,
 `cs2` 's bounds are not malformed (see
 xref:section_cap_malformed[xrefstyle=short]), and all reserved bits in `cs2` 's
 metadata are 0. <<CBUILDCAP>> is typically used alongside <<CSETHIGH>> to build
-capabilities from integer values. The case `cs1 == 0` trivially leads to the tag
-of `cd` being stripped.
+capabilities from integer values.
+
+NOTE: Although currently this will set the tag to 0 and leave the metadata
+otherwise unchanged when `cs1` is `c0`, this may change in future extensions,
+and so software should not assume this.
 
 Prerequisites::
 {cheri_base_ext_name}

Diff for: src/insns/wavedrom/cbuildcap.adoc

@@ -5,7 +5,7 @@
   {bits: 7,  name: 'opcode',  attr: ['7', 'OP=0110011'], type: 8},
   {bits: 5,  name: 'cd',      attr: ['5', 'dest'], type: 2},
   {bits: 3,  name: 'funct3',  attr: ['3', 'CBUILDCAP=101'], type: 8},
-  {bits: 5,  name: 'cs1',     attr: ['5', 'src1'], type: 4},
+  {bits: 5,  name: 'cs1',     attr: ['5', 'src1 != 0'], type: 4},
   {bits: 5,  name: 'cs2',     attr: ['5', 'src2'], type: 3},
   {bits: 7,  name: 'funct7',  attr: ['7', 'CBUILDCAP=0000110'], type: 3},
 ]}