Map Edge Extension shader errors

[abma]

happens with linux ati opensource drivers:

[f=0000000] Error: OpenGL: source<Shader> type<error> id<44> severity<high>:
0:16(2): error: assignment to read-only variable 'gl_Vertex'
[f=0000000] Error: OpenGL: source<Shader> type<error> id<45> severity<high>:
0:17(2): error: assignment to read-only variable 'gl_Vertex'
[f=0000000] Error: OpenGL: source<Shader> type<error> id<46> severity<high>:
0:30(6): error: LHS of `&&' must be scalar boolean
[f=0000000] Error: OpenGL: source<Shader> type<error> id<47> severity<high>:
0:32(10): error: if-statement condition must be scalar boolean
[f=0000000] Error: OpenGL: source<Shader> type<error> id<48> severity<high>:
0:34(10): error: if-statement condition must be scalar boolean
[f=0000000] [Map Edge Extension] Error: Map Edge Extension widget: mirror shader error: 0:16(2): error: assignment to read-only variable 'gl_Vertex'
0:17(2): error: assignment to read-only variable 'gl_Vertex'
0:30(6): error: LHS of `&&' must be scalar boolean
0:32(10): error: if-statement condition must be scalar boolean
0:34(10): error: if-statement condition must be scalar boolean

[abma]

after http://imolarpg.dyndns.org/trac/balatest/changeset/4990 :

[f=-000001] Error: OpenGL: source<Shader> type<error> id<44> severity<high>:
0:31(7): error: could not implicitly convert operands to relational operator
[f=-000001] Error: OpenGL: source<Shader> type<error> id<45> severity<high>:
0:31(7): error: LHS of `&&' must be scalar boolean
[f=-000001] Error: OpenGL: source<Shader> type<error> id<46> severity<high>:
0:31(24): error: could not implicitly convert operands to relational operator
[f=-000001] Error: OpenGL: source<Shader> type<error> id<47> severity<high>:
0:33(10): error: could not implicitly convert operands to relational operator
[f=-000001] Error: OpenGL: source<Shader> type<error> id<48> severity<high>:
0:33(10): error: if-statement condition must be scalar boolean
[f=-000001] Error: OpenGL: source<Shader> type<error> id<49> severity<high>:
0:35(10): error: could not implicitly convert operands to relational operator
[f=-000001] Error: OpenGL: source<Shader> type<error> id<50> severity<high>:
0:35(10): error: if-statement condition must be scalar boolean
[f=-000001] [Map Edge Extension] Error: Map Edge Extension widget: mirror shader error: 0:31(7): error: could not implicitly convert operands to relational operator
0:31(7): error: LHS of `&&' must be scalar boolean
0:31(24): error: could not implicitly convert operands to relational operator
0:33(10): error: could not implicitly convert operands to relational operator
0:33(10): error: if-statement condition must be scalar boolean
0:35(10): error: could not implicitly convert operands to relational operator
0:35(10): error: if-statement condition must be scalar boolean

[abma]

http://imolarpg.dyndns.org/trac/balatest/changeset/4992